Download Geology

European Shotfirer Standard
Education for Enhanced Mobility
– ESSEEM –
Geology
worked out and giving a lecture by
LEDAP-Laboratory of Energetics and Detonics,
University of Coimbra
Institute of Engineering of Porto| ISEP
Department of Geotechnical Engineering
Laboratory of Cartography and Applied Geology,
LABCARGA|ISEP
Slide 2
Geology competences required
• What is important the shotfire to know in rock blasting?
•
Understanding the factors that influence the response of rock
mass to drilling and blasting.
• Which capabilities shotfire should demonstrate?
• Basic knowledge and understanding of rock mass strength and
deformability of geological materials and the influence of their
properties on drilling and blasting.
• Basic understanding of geological classification of rocks and
their physical properties.
• Basic understanding of types of minerals and
properties.
their physical
Slide 3
Course planning
Contents
Time
(6 hours)
Earth’s crust and rock cycle
15 min
Composition, classes and properties of minerals
60 min
Classification of rocks
90 min
Physical properties of rock mass and their influence on drilling and
90 min
blasting
Key questions and discussion
60 min
Slide 4
Symbols to help students
Fundamental knowledge
Supplementary knowledge
Danger
To read more
Link
Slide 5
Contents
• Earth’s crust and rock cycle
• Composition, classes and properties of minerals
• Classification of rocks and physical properties
• Influence of rock mass properties on drilling and blasting
2 slides and 1 link
with more 1 slide
Slide 6
Earth’s crust
The crust represents less than 1% of the Earth volume and varies in
thickness from approximately 0 km beneath oceans to approximately
70 km beneath high mountain chains.
(0-70 km)
(70-2890 km)
Slide 7
Earth’s crust (cont.)
The crust is composed by three basic different types of rocks:
•
•
•
Igneous
Sedimentary
Metamorphic
Explanation how the three
rock types are related to
each other and how
Rock cycle
Igneous
rock
Sediment
Magma
Volcanic
eruption
Metamorphic
rock
Sedimentary rock
Slide 8
Contents
• Earth’s crust and rock cycle
• Composition, classes and properties of minerals
• Classification of rocks and physical properties
• Influence of rock mass properties on drilling and blasting
4 slides and 14 links
with more 45 slides
Slide 9
Main elements composition of
minerals found in the Earth’s rocks
Percent Weight in Earth's Crust
Fe
Ca
Na K Mg
Al
O
Si
Periodic Table
Slide 10
Rocks - an aggregate of minerals
•
Monomineralic rocks
 Marble
 Quartzite
•
Polymineralic rocks
 Granite
 Gneiss
Slide 11
Main classes of minerals
Silicates (quartz, feldspar, mica, pyroxene, amphibole, olivine)
Carbonates (calcite, dolomite)
Sulfides ( pyrite, chalcopyrite, arsenopyrite)
Oxides and hydroxides (magnetite, hematite, limonite )
Native elements (copper, gold)
Mineral properties are fundamental to understand and
assess to the different types of rocks
Slide 12
Physical properties of minerals
Hardness
Streak
Cleavage
Luster
Fracture
Colour
Density
Crystal habit
Slide 13
Contents
• Earth’s crust and rock cycle
• Composition, classes and properties of minerals
• Classification of rocks and physical properties
• Influence of rock mass properties on drilling and blasting
3 slides and 17 links
with more 93 slides
Slide 14
Type of rocks
Variety of rocks
are observed namely by their mineral
composition, colour, texture, permeability and grain size.
Types of rocks:
Igneous
• Extrusive
• Intrusive
Sedimentary
Metamorphic
Slide 15
Rock main composition minerals
IGNEOUS *
SEDIMENTARY
METAMORPHIC
Quartz *
Quartz *
Feldspar group *
Mica group*
Clay
minerals Feldspar group *
group *
Feldspar group*
Mica group *
Pyroxene group*
Calcite
Garnet group *
Amphibole group*
Dolomite
Pyroxene group *
Gypsum
Staurolite *
Halite
Kyanite *
*
Quartz *
Silicate minerals
Slide 16
Physical properties of rocks
Structure
Weathering
Texture
Fracture
Density
Mechanical resistance
Composition
Water content
Porosity
Internal friction
Abrasiveness
Conductivity
Elasticity
Plasticity
Slide 17
Contents
• Earth’s crust and rock cycle
• Composition, classes and properties of minerals
• Classification of rocks and physical properties
• Influence of rock mass properties on drilling and
blasting
22 slides
Slide 18
Influence of structural patern
•
The structural pattern of the rock exerts a major influence
on fragmentation in many blasting situations
•
Blasting patterns should be designed to take advantage
of rock structure where possible
Slide 19
Importance of
geologic structure reporting
• The existence of bedding planes, schistosity, joints,
faults, contacts or other geologic structure that may
interfere with the confinement and distribution of explosive
energy within the rocks mass should be reported to the
shotfire.
• A detailed drill log, indicating discontinuities at various
depths, is essential for determining zones of weakness.
• The existence of cracks in the stemming zone will direct
or even dictate the fragmentation size.
• Oversize fragmentation, high bottom, overbreak and /or
unstable highwalls can be a result if widely separated
structure exist in certain types of rock.
Slide 20
Flyrocks cases
Flyrocks from
unsuitable stemming
Flyrocks
Go to 7.3.2 in WP6
Slide 21
Widely separated
structures effect
Open or widely separated structures can result in:
•
Slow drill penetration rates related to poor hole and
hole deviation may be concern.
•
Poor fragmentation due to:
 Interruption of the explosive generated stress
waves;
 Disruption of confinement.
 If explosives energy is not contained within
the rock mass, bouldering or oversize will
occur. Venting or airblast can occur in these
zones.
Slide 22
Oversized fragmentation
• Oversized fragmentation can occurs when exists a lack of
pre-existing fractures or micro-fractures in the top portion
of the rock face between beds or joints.
• Explosive energy is not distributed to these areas.
• Oversized fragmentation and bad endbreak may occur
when strike is parallel to the free face.
Slide 23
Effect of the angle between
strike and free surface
• It is a good practice to design a shot so that the strike of
the structure is at an angle to the free surface.
 Structures, such as joints or faults, at an angle to the
free surface typically contribute to better fragmentation
with successful endbreak.
Slide 24
Effect of the angle between
strike and free surface
• A strike perpendicular to
the free surface would
result in structures, such
as joints or faults,
perpendicular to the
face which may cause
blocky breakage, litle
endbreak.
• A strike parallel to the
free surface may cause
oversized fragmentation
and bad endbreak.
Free surface
Free surface
Slide 25
Influence of density of
rock of intact rock
•
Density often indicates the difficulty to be expected in
breaking rock with the denser material responding best
to explosives with high detonation pressures.
•
Density of rock material are often related to the porosity of
the rock. Porosity describes how densely the material is
packed.
 Less dense - more porous rocks absorb energy in ways
that make control of fragment size and gradation difficult.
Slide 26
Influence of texture of intact rock
•
Fabric directions, particularly in granite, were used to the
advantage of the quarry man as favorable or unfavorable
planes for breaking out rock materials.
•
Blasting patterns might be designed to break rock
preferentially along weak fabric directions so as to
reduce powder factor or increase spacing provided the
desired product is obtained.
Slide 27
Influence of
discontinuities in a rock mass
•
Any mechanical discontinuity in a
rock mass result in zero or low
tensile strength.
•
It is the collective term for most types
of joints, bedding planes, schistosity,
faults, shear zones.
Most rock masses are discontinuity
controlled, by one, two, or three sets
of primary regional systematic
discontinuities (like joints, faults,…)
(Ref: http://web.mst.edu/~rogersda/)
Slide 28
Joint Frequency
• In rock removal blasting, closely spaced (or
fractured intercept) joints can mean a savings in
blasting costs because it will not be necessary to
use a sizable part of the energy in fracturing
•
More effective fragmentation is accomplished where
explosive charges lie within the solid blocks bounded by
joints
•
In quarrying highly fractured material, the fragment size of
the product will approximate that of the natural fragment,
and of course, no quarrying should be attempted where
the natural fragment size falls below that desired
Slide 29
Orientation of joints
• Blasting technique may need modifications to fit joint
orientations. Stability of the excavation is of
upmost importance and till take priority over
questions of economics, such as are involved in
blasting
• Idealized systems of fractures may sometimes be
predicted for the more common geological settings
expected on construction jobs
• The simplest is an orthogonal system that can be
expected in flat-lying sedimentary strata.
 This system consists of horizontal joints parallel to
the bedding and one or ho sets of vertical joints
Slide 30
Orientation of joints (cont.)
•
The free face may be carried parallel rather than perpendicular to
major vertical joints. Not only are large fractures already developed
in the major direction, but it can also be expected to be a potentially
weak direction in which additional blast fracturing will take place
•
In massive (unbedded) rock such as granite, the fracture system is
believed to have been determined by regional stresses in the
remote geological past. It will commonly consist of nearly vertical
joints in two sets striking at right angles. A third set of nearly
horizontal sheeting joints may also be present
•
Excavation should be designed where possible to take advantage of
the natural joint system, and due caution exercised for overbreakage on natural joints well back from the lip of the excavation.
The frequency of fractures in massive rocks is low and
consequently blasting problems usually are less acute
Slide 31
Range of discontinuities
and their influence
Discontinuities constitute a tremendous range, from structures
which are sometimes thousands of meters in extent down to - per
definition - mm size.
Slide 32
The importance of location and
orientation of discontinuities
The distribution and
orientation of
discontinuities, such as
bedding planes, faults
and joints, is equally
important.
In the two cases permit
sliding of the foundation
under the bridge because it
daylights in (i.e. intersects)
the slope face.
Discontinuity B, with similar
characteristics to
discontinuity A, would not
pose a hazard even though it
has a similar orientation
because it does not daylight.
(after Price, 2009)
Slide 33
The importance of location and
orientation of discontinuities
The distribution and
orientation of
discontinuities, such as
bedding planes, faults
and joints, is equally
important.
In the two cases permit
sliding of the foundation
under the bridge because it
daylights in (i.e. intersects)
the slope face.
Discontinuity B, with similar
characteristics to
discontinuity A, would not
pose a hazard even though it
has a similar orientation
because it does not daylight.
(after Price, 2009)
Slide 34
General range of
strengths for common rock types
(Ref: Price, 2009)
Slide 35
Rock strength comparison
Adapted from J. Zhao, 2009
Slide 36
Influence of weathering on
rock mass properties
• All rock is jointed media.
• The orthogonal jointing pattern is
usual.
• Groundwater moves through the
joints.
• Joints often occur in semi-parallel
clusters, which are more subject to
weathering and disintegration;
enlarging flow conduits.
Lavadores jointed granitic rock mass exposure, N
Portugal (aerial photo credits: F. Piqueiro)
Slide 37
Weathering influence
The weathering, for blasting purposes, effect is twofold.
•
•
First, the properties of the rock are altered, and
Second, this change of properties is localized in a layer
parallel to the ground surfaces so that crude horizon is
developed
•
One way of simplifying the handling of weathered material blast and
excavate it in one or two lifts apart from material below.
•
Upper lifts might respond to lower velocity explosives for best
impedance matching and efficiency. In the transition zones and in the
fresh rock below, detonation velocity might be increased farther.
•
Some weathered rocks are so decomposed that they can be treated
as soil and excavated without blasting.
Slide 38
Groundwater
•
Water content is a measure indicating the amount of water the rock
material contains. It is simply the ratio of the volume of water to the
bulk volume of the rock material.
•
Zones of various degrees of saturation by groundwater, for blasting
purposes, form another type of crude horizon parallel to the ground
surface, with properties varying accordingly
•
Saturated zones require explosives with greater water resistances and
necessitate more care in stemming. Unsaturated material above the water
table should be blasted separately from that in the capillary zone and below
where reasonable
•
After removal of the unsaturated material, however, it should be verified that
the material yet to be excavated is still saturated. Disturbance during
excavation may have caused groundwater to migrate. Fluctuations from rainy
to dry seasons should be considered also
Slide 39
Main variables influencing rock
properties and behaviour
Ref:Palmström, 1995
Slide 40
References
Basic references
Hoek, E. 2007. Practical rock engineering. RocScience: Hoek’s Corner,
342 p.
Brady, B. H. G. & Brown, E. T. 2004. Rock mechanics for underground
mining. Kulwer Academic Publishers, Dordrecht. 628 p.
Langefors U. & Kihlstrom B. 1978. The modern technique of rock
blasting. John Wiley & Sons Inc; 3rd edition, 438 p.
Price, D. J. 2009. Engineering Geology: principles and practice.
Springer. 450 p.
Frank Press, Raymond Siever, John Grotzinger and Thomas H. Jordan
2006. Understanding Earth. 4th edition, 588 p.
Slide 41
References
Advanced references
Bieniawski, Z. T. 1989. Engineering rock mass classifications: a
complete manual for engineers and geologists in mining, civil, and
petroleum engineering. Interscience, John Wiley & Sons, 272 p.
ISRM–International Society for Rock Mechanics 2007. The complete
ISRM suggested methods for characterization, testing and
monitoring: 1974-2006. In: Ulusay, R. & Hudson, J.A. (eds.), suggested
methods prepared by the Commission on Testing Methods, ISRM. Ankara,
Turkey. 628 p.
Geomechanics, rock mechanics, geo-engineering related links
http://www.rocscience.com/hoek/Hoek.asp
http://www.rockmass.net/
http://www.geoengineer.org/
http://www.isrm.net
http://www.iaeg.info/
Slide 42
Carbonates
• Carbonates are minerals made of carbon and oxygen in
the form of the carbonate anion (CO32-) in combinations
with calcium and magnesium.
• Calcite is one of such mineral.
• The carbonates are among the most widely distributed
minerals in the Earth’s crust.
Slide 1
Carbonates
Calcite
Slide 2
Carbonates
Calcite
Slide 3
Carbonates
Dolomite
Slide 4
Carbonates
Dolomite
Slide 5
Native elements
• Native element minerals are those elements that
occur in nature in uncombined form with a distinct
mineral structure.
• There are only about 20 elements that can be found in
a native state. These elements can be divided into
three sub-groups, metals, semimetals, and nonmetals.
 The metal group is the more common.
Slide 1
Native elements
Copper native
Slide 2
Native elements
Gold native
Slide 3
Oxides and hydroxides
• Oxides are compounds of the oxygen anion (O2-) and metallic
cations.
• An example is the mineral hematite.
• Oxide minerals are extremely important in mining as they form
many of the ores from which valuable metals can be extracted.
• They also carry the best record of changes in the Earth's magnetic
field.
• Common oxides include hematite (iron oxide), magnetite (iron
oxide), chromite (iron chromium oxide), spinel (magnesium
aluminium oxide – a common component of the mantle), ilmenite
(iron titanium oxide), rutile (titanium dioxide), and ice (hydrogen
oxide).
Slide 1
Oxides
Magnetite
Slide 2
Oxides
Hematite
Slide 3
Silicates
• Silicates, the most abundant minerals in the Earth’s crust,
are composed of oxygen (O) and silicon (Si) - the most
abundant elements in the crust - mostly in combination
with the cations of other elements.
• The silicates are the largest, the most interesting and by
far the most complicated class of minerals. Approximately
30% of all minerals are silicates and some geologists
estimate that 90% of the Earth's crust is made up of
silicates.
Slide 1
Silicates
• Silicate is a chemical term for the group of a single atom of
silicon surrounded by four atoms of oxygen, or SiO4, in the
shape of a tetrahedron.
• The complicated structures that these silicate tetrahedrons
form is truly amazing.
• They can form as single units, double units, chains, sheets,
rings and framework structures.
Slide 2
Silicates
Quartz
Slide 3
Silicates
Feldspar
Slide 4
Silicates
Mica
Slide 5
Silicates
Pyroxene
Slide 6
Silicates
Amphibole
Slide 7
Silicates
Olivine
Slide 8
Single tetrahedron
• Isolated (single) tetrahedron - Isolated tetrahedral are linked by the
bonding of each oxygen ion of the tetrahedron to a cation. The
cations, in turn, bond to the oxygen ions of other tetrahedral. The
tetrahedral are thus isolated from one another by cations on all
sides. Olivine is a rock-forming mineral with this structure.
http://web.visionlearning.com/silica_molecules.shtml
Slide 1
Single chains
• Single-Chain Linkages - Single chains also form by sharing oxygen
ions. Two oxygen ions of each tetrahedron bond to adjacent
tetrahedral in an open-ended chain. Single chains are linked to other
chains by cations; examples are the iron an magnesium ions or
both.
http://web.visionlearning.com/silica_molecules.shtml
Slide 2
Double chains
• Double-chain linkages - Two single chains may combine to form
double chains linked to each other by shared oxygen ions. Adjacent
double chains linked by cations form the structure of the amphibole
group of minerals.
http://web.visionlearning.com/silica_molecules.shtml
Slide 3
Sheets
• Sheet linkages - In sheet structures, each tetrahedron shares three
of its oxygen ions with adjacent tetrahedral to build stacked sheets
of tetrahedral. Cations may be interlayered with tetrahedral sheets.
The micas and clay minerals are the most abundant sheet silicates.
http://web.visionlearning.com/silica_molecules.shtml
Slide 4
Three-dimensional networks
• Frameworks - three-dimensional frameworks form as each
tetrahedron shares all its ions with other tetrahedral. Feldspars, the
most abundant group of minerals in Earth’s crust, are framework
silicates, as is another of the most common minerals, quartz.
http://web.visionlearning.com/silica_molecules.shtml
Slide 5
http://stevekluge.com/geoscience/images/silicates.jpg
Slide 6
Sulfides
• A sulfide mineral is a mineral containing sulfide (S2-) as the
major anion.
• Sulfide minerals comprise (by weight) about 0,15 percent of the
earth’s crust.
• More than 200 sulfide mineral varieties are known.
• The main species-forming elements of sulfide minerals are Pb,
Cu, Sb, As, Ag, Bi, Fe, Co, and Ni, which are the components of
dozens of mineral species.
• Most sulfide minerals are optically opaque, and they often have
high reflectivity. Their hardness on Mohs’ scale usually ranges
from 2 to 4. The density of sulfide minerals is greater than 4000
kg/m3
Slide 1
Sulfides
Pyrite
Slide 2
Sulfides
Chalcopyrite
Slide 3
Cleavage
Crystal cleavage - tendency of a crystal to break along flat
planar surface.
Cleavage
occurs
in
minerals
that
have
specific
planes
of
weakness. These planes
or directions are inherent
in the structure of the
mineral and form from a
variety of factors.
First
cleavage
is
reproducible, meaning that
a crystal can be broken
along the same parallel
plane over and over again.
Slide 1
Cleavage
• All cleavage must parallel a possible crystal face.
 This means that the crystal could have a crystal face parallel to
its cleavage, but these faces are not always formed.
 All cleavage planes of a mineral must match that mineral's
symmetry.
 The same mineral will always have the same cleavage.
• Cleavage is poor if bonds in crystal structure are strong, good
if bonds are weak.
• Covalent bonds generally give poor or no cleavage; ionic
bonds are weak and so give excellent cleavage.
Slide 2
Colour
• The colour of a mineral is one of its most obvious attributes, and is
one of the properties that is always given in any description.
• Colour results from a mineral’s chemical composition, impurities
that may be present, and flaws or damage in the internal structure.
Unfortunately, even though colour is the easiest physical property
to determine, it is not the most useful in helping to characterize a
particular mineral.
•
•
Some minerals do have only a single colour that can be diagnostic, as for
instance the yellow of sulphur. Also, although many minerals vary in colour
few span the spectrum of colours as fluorite does. Often we find most
colour variations of a given mineral are consistently light coloured (white,
tan, pink, yellow) or dark coloured (gray, black, blue, green).
Colour is determined by kind of atoms or ions and trace impurities. Many
ionically bonded crystals are colourless. Iron tends to colour strongly.
Slide 1
Identify colour
• Experts use colour all the time because they have learned the usual
colours and the usual exceptions for common minerals.
• If you're a beginner, pay close attention to colour but do not rely on
it. First of all, be sure you aren't looking at a weathered or tarnished
surface, and examine your specimen in good light.
• Colour is a fairly reliable indicator in the opaque and metallic
minerals - for instance the blue of the opaque mineral lazurite or
the brass-yellow of the metallic mineral pyrite. In the translucent or
transparent minerals, colour is usually the result of a chemical
impurity and should not be the only thing you use. Olivine, for
example, is distinctly green. Other minerals, such as quartz, can
take on multiple colours. It is colourless in its pure form, but due
to some compositional variations, it can also be black, brown, pink,
green, purple or opalescent blue.
Slide 2
Identify colour
When
identifying
the
colour of a mineral is
difficult, one can also look
at the colour of the mineral
in powder form. This is
most easily achieved by
scraping
the
mineral
against
a
piece
of
unglazed porcelain and
observing the colour of the
powder streak left behind
on the porcelain.
Slide 3
Crystal habit
• Crystal habit is a description of the shapes and aggregates that a
certain mineral is likely to form. The term "crystal habit" is used to
categorize the appearance, shape, and size of a crystal, and
identify its unique growth characteristics that result from its
crystalline structure and growth environment.
• Although most minerals do have different forms, they are
sometimes quite distinct and common only to one or even just a
few minerals.
• There are basically two major divisions to keep in mind when
discussing crystal habits.


First, there are crystallographic forms whose names often separate the true
Rock Hounds from the amateurs. These crystal forms are controlled by the
structure and therefore the symmetry of the crystal.
Secondly there are more descriptive terms that quickly portray the character
of the crystal or aggregate crystals. The shape and character of the aggregate
may be just as distinctive as an individual crystal's shape.
Slide 1
Crystal habit
• Some habits are distinctive of certain minerals, although most
minerals exhibit many differing habits (the development of a
particular habit is determined by the details of the conditions during
the mineral formation/crystal growth). Crystal habit may mislead the
inexperienced as a mineral's internal crystal system can be hidden
or disguised.
• Crystal habit depends on planes of atoms or ions in a mineral’s
crystal structure and the typical speed and direction of crystal
growth.
Slide 2
Factors influencing
crystal’s habit
• Factors influencing a crystal's habit include: a combination of two or
more crystal forms; trace impurities present during growth; crystal
twinning and growth conditions (i.e., heat, pressure, space).
• Minerals belonging to the same crystal system do not necessarily
exhibit the same habit. Some habits of a mineral are unique to its
variety and locality.
• There are approximately thirty-six standardized terms to describe
the variations, or habits of a crystal's growth. A particular mineral
may exhibit several different habits, all of which are influenced by
the following factors:
 1. Crystal Twinning ( two individual crystals share some of the same
crystal lattice points)
 2. Growth Conditions (heat, pressure, and space)
 3. Trace Impurities (present during crystal formation)
Slide 3
Crystal´s habit
Amethist-quartz
Slide 4
Density
• The rock density is commonly expressed in kg/m3 (SI). Other units
are gram per cubic centimetre (g/cm3) or tonnes per cubic meter
(t/m3).
• Relative density is an a-dimensional number and expresses the
density of the rock relative to the density of the water.
• Density depends on atomic weight of atoms or ions and their
closeness of packing in crystal structure. Iron minerals and metals
have high density; covalently bonded minerals have more open
packing and so have lower density.
• Rocks are typically about three times denser than water, so a
volume of rock will weigh about three times more than the same
volume of water.
•
Slide 1
Fracture
• Fracture is a description of the way a mineral tends to break along
a regular surface under then cleavage plans. It is different from
cleavage and parting which are generally clean flat breaks along
specific directions. Fracture occurs in all minerals even ones with
cleavage, although a lot of cleavage directions can diminish the
appearance of fracture surfaces.
•
Fracture type is related to distribution of bond strengths across irregular
surfaces other than cleavage planes.
•
Different minerals will break in different ways and leave a surface that can
be described in a recognizable way.
•
Although many minerals break in similar ways, some have a unique
fracture and this can be diagnostic.
•
The most common fracture type is conchoidal. This is a smoothly curved
fracture that is familiar to people who have examined broken glass.
Slide 1
Conchoidal fracture
Conchoidal
fracture in
quartz
The most common fracture type is conchoidal.
This is a smoothly curved fracture that is familiar to people who have
examined broken glass.
Slide 2
Hardness
• Hardness - measure of the ease with which the surface of a
mineral can be scratched.
 Just as a diamond, the hardness mineral known scratches
glass, so a quartz crystal which that is harder than feldspar,
scratched a feldspar crystals.
•
Strong chemical bonds give high hardness.
•
Covalently bonded minerals are generally harder than
ionically.
Slide 1
Mohs scale of hardness
Slide 2
Mohs scale of hardness
Mohs
hardness
Mineral
Absolute
Hardness
1
Talc
(Mg3Si4O10(OH)2
1
2
Gypsum
(CaSO4·2H2O)
3
3
Calcite
(CaCO3)
9
Image
Slide 3
Mohs scale of hardness
Mohs
hardness
4
5
6
Mineral
Flurite
(CaF2)
Apatite
(Ca5(PO4)3(OH-,Cl-,F-))
Orthoclase Feldspar
(KAlSi3O8)
Absolute
Hardness
Image
21
48
72
Slide 4
Mohs scale of hardness
Mohs
hardness
Mineral
Absolute
Hardness
7
Quartz
(SiO2)
100
8
Topaz
(Al2SiO4(OH-,F-)2)
200
9
Corundum
(Al2O3)
400
Image
Slide 5
Mohs scale of hardness
Mohs
hardness
10
Mineral
Diamond
(C)
Absolute
Hardness
Image
1600
Slide 6
Luster
• The luster of a mineral is the way its surface reflects light. It will be
necessary, at least at first, only to distinguish between minerals with
a metallic luster and those with one of the non-metallic lusters.
• A metallic luster is a shiny, opaque appearance similar to a bright
chrome bumper on an automobile.
• Other shiny, but somewhat translucent or transparent lusters
(glassy, adamantine), along with dull, earthy, waxy, and resinous
lusters, are grouped as non-metallic.
• Luster should not be confused with color: A brass-yellow pyrite
crystal has a metallic luster, but so does a shiny grey galena crystal
- Quartz is said to have a glassy (or vitreous) luster, but its color may
be purple, rose, yellow, or any of a wide range of hues.
• Luster tends to be glassy for ionically bonded crystals, more
variable for covalently bonded crystals
Slide 1
Luster
– It is related to transparency, surface
conditions, crystal habit and index
of refraction. Most terms used to
describe luster are self-explanatory:
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Adamantine - very gemmy crystals
Dull - just a non-reflective surface of any
kind
Earthy - the look of dirt or dried mud
Fibrous - the look of fibers
Greasy - the look of grease
Gumdrop - the look a sucked on hard
candy
Metallic - the look of metals
Pearly - the look of a pearl
Pitchy - the look of tar
Resinous - the look of resins such as dried
glue or chewing gum
Silky - the look of silk, similar to fibrous but
more compact
Submetallic - a poor metallic luster, opaque
but reflecting little light
Vitreous - the most common luster, it
simply means the look of glass
Waxy - the look of wax
Adamantine luster
Silky luster
Pyrite
Metallic luster
Pearly luster
Slide 2
Cleavage/Luster
Simplified classification of mineral laboratory samples
Cleavage
Metallic
4 directions
3 directions at 90º
Non-Metallic/Dark
Non-Metallic/Light
Fluorite
Fluorite
Galena
Halite
3 directions at 75º
and 105º
Calcite
2 directions at 90º
Pyroxene/
Ca-Plagioclase
2 directions at 56º
and 124º
Amphibole
1 direction
No cleavage
Pyrite/Hematite
K-Feldspar
/Na-Plagioclase
Biotite
Muscovite
Hematite/Limonite/
Quartz/Olivine
Quartz/Olivine
Slide 3
Streak
The colour of a mineral when it is powdered is called the streak of the
mineral. Crushing and powdering a mineral eliminates some of the
effects of impurities and structural flaws, and is therefore more
diagnostic for some minerals than their colour. Streak can be
determined for any mineral by crushing it with a hammer, but it is more
commonly (and less destructively) obtained by rubbing the mineral
across the surface of a hard, unglazed porcelain material called a streak
plate.
The colour of the powder left behind on
the streak plate is the mineral's streak.
The streak and colour of some minerals
are the same. For others, the streak may
be quite different from the colour, as for
example the red-brown streak of
hematite, often a gray to silver-gray
mineral.
Slide 1
http://zebu.uoregon.edu/
Slide 1
Abrasiveness
• The abrasiveness is the ability of the rock to weathering
the contact surface, like the perforation tools during drill
process.
• The abrasiveness of the rocks depends of the hardness,
shape and grain size (eg. Rocks with quartz are normally
abrasives).
• The porosity of the rocks reduce its abrasiveness.
• Although the polymineral rocks to have the same hardness
they have higher abrasiveness than monomineral rocks.
Slide 1
Composition of rocks
• Rock composition refers to the percentages of minerals
contained in the rock.
• A main determining factor in the formation of minerals in a rock
mass is the chemical composition of the mass. For a certain
mineral can be formed only when the necessary elements are
present in the rock.
–
–
Calcite is most common in limestones and marbles, as these consist
essentially of calcium carbonate;
Quartz is common in sandstones and in certain igneous rocks which
contain a high percentage of silica.
• Other factors are of equal importance in determining the natural
association or paragenesis of rock-forming minerals, principally the
mode of origin of the rock and the stages through which it has
passed in attaining its present condition.
–
Two rock masses may have very much the same bulk composition
and yet consist of entirely different assemblages of minerals. The
tendency is always for those compounds to be formed, which are
stable under the conditions under which the rock mass originated.
Slide 1
Electrical conductivity
• Electrical conductivity (formation factor) is the rock's capacity to
transmit electrical current.
• The electrical conductivity of a rock can be reasonably approximated
from the measured conductivities of the major mineral constituents.
• Where the approximation shows lesser agreement with recent
geophysical electrical conductivity models, particularly at transition
zone depths, consideration of the effects of minor constituents that
might affect the electrical properties of minerals is required.
Leak of current may exist when
detonators are placed into the drillholes
of rocks with a considerable electrical
conductivity value
Slide 1
Density of rocks
Range of density relative of rocks
•
The density and resistance of rocks have
normally good correlation. In general rocks
with low density deforming and rupturing
easily.
•
Rocks of the same type can have any density
in a range of densities, since they can contain
different proportions of minerals and voids.
Rock density is very sensitive to the minerals
that compose a particular rock type.
•
 Sedimentary rocks (and granite), which are
rich in quartz and feldspar, tend to be less
dense than volcanic rocks.
 More mafic a rock is, the greater its density.
Slide 1
Elasticity
• An elastic property is the measurement of the tendency of a rock
to deform non-permanently in various directions when stress is
applied.
• Many fresh, hard rocks are elastic when considered as laboratory
specimens. But on the field scale rocks can be expected to contain
fractures, fissures, bedding planes, contacts, zones of altered rock
and clays with plastic properties.
•
Therefore, most rocks do not exhibit perfect elasticity. The
extent of irrecoverability of strain in response to load cycles
may be important for the design and can be determined by the
slope of the load/deformation curve.
Slide 1
Laboratory stress-strain curves
Stress vs. Strain curve typical of structural
steel
1. Ultimate Strength
2. Yield Strength – Elastic limit
3. Rupture
4. Strain hardening region
5. Necking region.
A: Apparent (Engineering) stress (F/A0)
B: Actual (True) stress (F/A)
Slide 2
Elasto-plastic deformation
Intact rock (solid material between
discontinuities) is an elasto-plastic material,
subject to elastic recovery and permanent
deformation (see Stress vs Strain plot)
Mohr Circles are the most common
technique used to describe the failure
envelope and the strength parameters
friction and cohesion
(after http://web.mst.edu/~rogersda/)
Rock tends to exhibit a slightly curva-linear
failure envelope with low tensile strength,
shown at upper right
Slide 3
Strain incompatibility
Strain Incompatibility
The most important
feature of
geomechanics is
appreciating the strain
incompatibility
between rocks of
dissimilar stiffness,
strength, and
deformability (such as
shale and sandstone)
Shale seam between
sandstone beds
(after http://web.mst.edu/~rogersda/)
Slide 4
Variances in rock stiffness
(after http://web.mst.edu/~rogersda/)
Variances in rock stiffness plays a significant role in controlling fracture spacing
between tensile discontinuities
Hard rocks can be more brittle, and thereby, exhibit closer fracture spacings
Slide 5
Test results vs rock characteristics
• Most rocks are brittle,
and break under
induced tension when
compressed
• Even modest lateral
confinement can exert
significant increase in
observed strength.
• This is why tensile
reinforcement provided
by rock bolts can be so
effective
(after http://web.mst.edu/~rogersda/)
Slide 6
Crack propagation
Typical sequence of crack
propagation observed
during an unconfined
compression test on intact
rock, with joints or partings.
Extension fractures form
parallel to the maximum
principal stress, which is
vertical
(after http://web.mst.edu/~rogersda/)
Slide 7
Fracture
• A fracture is any local separation or discontinuity plane in a
geologic formation, such as a joint or a fault that divides the rock
into two or more pieces.
• Fractures are commonly caused by stress exceeding the rock
strength. Fractures can provide permeability for fluid movement,
such as water or hydrocarbons.
• Highly fractured rocks can make good aquifers or hydrocarbon
reservoirs, since they may possess both significant permeability
and fracture porosity
Slide 1
Internal friction
• Express the ability of rock to absorb the tension of shock wave
induced by detonation.
• The angle of internal friction measures the ability of a material
(could be rock or soil or whatever) to withstand a shear stress.
 It is the angle(q) measured between the normal force (N) and
resultant force (R), that is attained when failure just occurs in
response to a shearing stress (FII).
q – Angle of internal friction
Slide 1
Internal friction
• Experimental results in the published literature show that at low
normal stress the shear stress required to slide one rock over
another varies widely between experiments.
• This is because at low stress rock friction is strongly dependent on
surface roughness. At high normal stress that effect is diminished
and the friction is nearly independent of rock type.
Slide 2
Mechanical resistance
• Mechanical resistance to compression and traction are used as a
way to assess the ability of the rocks to blast.
• The strength of a rock is the amount of pressure it can withstand
without breaking.
• There are three kinds of forces in breaking of materials: tension
(pulling apart), compression (pushing together) and shear (sliding
apart).
• When a bar of material is pushed down, the bending causes
compression on the top and tension on the bottom.
• One standard measure of strength of a material, independent of the
size of the sample, is the "modulus of rupture."
 It indicates the strength of the rock when a bar of rock is
pushed down until it breaks in half, based on the dimensions
of the rock and the force required to break it.
Slide 1
Loading configurations
Slide 2
Slide 3
Plasticity
• The plasticity of rocks express the deformation when the field’s
tension go above the elastic limit.
• Plasticity depend of mineral composition.
• When quartz, feldspar and other hard minerals increase in the
rock the plasticity is decreasing.
Slide 1
Porosity
• Porosity is defined as the ratio of the void volume in the rock to
the total volume of the rock.
• This void space consists of pore space between grains or
crystals, in addition to crack space.
• In sedimentary rocks, the amount of pore space depends on the
degree of compaction of the sediment (with compaction generally
increasing with depth of burial), on the packing arrangement and
shape of grains, on the amount of cementation, and on the
degree of sorting.
•
Porosity is measured in percents of fractions of one. For
example, if one cubic centimeter of rock contains 0,25 cubic
centimeters of void, the porosity is 25% or 0,25.
Slide 1
Type of porosity
There are two types of porosity:
• Integranular porosity – corresponds to the space between
grains of sediment. It is almost uniform in the rock.
•
Post-formation porosity – corresponds to the voids and
cavities produced by the dissolution of rock from
underground water. The voids have higher size and the
distribution is less uniform as integranular porosity.
Slide 2
Slide 3
Structure of the rock
• Rock structure: described the features produced in the
rock by movements during and after its formation. Rock
structure is the result of what has happened to rock over
millions, even billions of years.
Slide 1
Structure of the rock
• There are hundreds of distinct rock structures. Geologists
find it convenient to divide them into 'primary' and 'secondary'
structures.
 Primary structures: structures formed before or at the same as
material is in the process of becoming rock.
 For example, formed as magma crystallizes or as
sediment accumulates.
 Secondary structures: structures imposed on rock after it has
already formed.
 For example, formed as a result of compression of existing
rock.
Slide 2
Major types of structural features
Brief description of the major types of
structural features:
i)
non-tectonic structures: bedding
planes
ii) tectonic structures: folds, faults,
shear zones, joints
The hardest rocks are perturbed by
discontinuities; such as these
joints, which are essentially tensile
fractures, which form a never ending
series of blocks
Slide 3
Structure of the rock
•
Rock structure: described the features produced in the rock
by movements during and after its formation. Rock structure
is the result of what has happened to rock over millions, even
billions of years.
•
Rock structure vary on larger scales.
•
Examples of structures include:
 Bedding;
 Schistosity;
 Joints;
 Faults;
 Contacts.
•
The geometric characteristics of and relationships between
these small-scale rock features constitute rock texture.
Slide 4
Types of rock structure
Folds and faults
Horizontal bedding planes
Strain
Primary structure
Primary
structure
(non-tectonic)
(non-tectonic)
Horizontal bedding planes
Secondary structure
Secondary
structure
(tectonic)
(tectonic)
Folds and faults
Slide 5
Folds
Folds:
Any continuously curved boundary
structure in a rock
Slide 6
Faults
Faults - a fracture in rock in which one side slides laterally
past the other with a displacement that is greater than the
separation between the blocks on either side of the fracture.
Slide 7
Reverse fault
Block before fault
Fault plane
Strike-slip fault
Normal fault
Oblique-slip fault
Slide 8
Faults
Faults:
Fractures which have had a displacement of the rocks along
them
Slide 9
Fault and Crush zones
•
Fault zones may consist of a series of sub-parallel faults,
anastomosing, and enclosing slabs of wall rock or lenses of
crushed rocks (breccias).
•
Blasting conducted near faults will often break to the fault
surface.
•
Fault zones (and breccia) by virtue of their high porosity can
also have a cushioning effect on crushing and seismic waves.
In such materials, the blasting technique might be modified to
the extent that little seismic energy is provided. An explosive
with a low detonation velocity might be most satisfactory.
•
•
Porous faults and breccias constitute potentially weak zones
that-may be of utmost importance in stability consideration.
Slide 10
Bedding and faults effects
Bedding effect:
• It is a helpful to the blaster in achieving a desired floor, wall
or slope profile.
 When the beds are tight;
 In close layers, approaching the desired fragmentation
size.
Faults effect:
• Faults can decrease drill penetration rates
by causing drill bits and steel to wander or
to bind in the hole.
• Faults can cause overbreak or backbreak
to a fault plane.
• Venting could occur if weakly cemented
material within the fault zone does not
contain explosive energy during a blast.
Slide 11
Schistosity
• Schistosity: refers to layering which occurs in metamorphic
rocks.
• It is associated with alignment of “platey” minerals such
as mica.
• The alignment of platey, weakly bonded minerals
greatly reduces the tensile strength of the rocks mass
and consequently is a helpful in fragmentation.
Slide 12
Joints
• Joints: cracks or fractures in rock with no associated
displacement.
• A joint can be intersecting with, as well as perpendicular or
parallel to, bedding planes or schistosity.
• The spacing of joints is typically a good predictor of post-blast
fragment size, specifically in areas of which there is poor or no
explosives energy distribution.
Go to 7.2.2 in WP6
Slide 13
Joints classification
Joints can be classified into three groups:
• Strike joints: joints which run parallel to the direction of
strike of country rocks are called "strike joints“.
• Dip joints: joints which run parallel to the direction of dip
of country rocks are called "dip joints“.
• Oblique joints: joints which run oblique to the dip and
strike directions of the country rocks are called "oblique
joints".
Slide 14
Joints classification
Slide 15
Joints
They are formed by tectonic stressing and are developed in
nearly all rocks
Granitic jointed rock mass (Porto, Portugal)
Metasedimentary jointed
rock mass (Trofa, Portugal)
Slide 16
Block shapes or jointing pattern
Slide 17
Contacts between
different rock types
A contact may exist where a sedimentary and an igneous unit
meet.
• Contact will greatly affect drill and blast
implementation if a contact exist between two rock
types of drastically different physical property.
Metamorphic rocks
Sedimentary rocks
Slide 18
Shear zones
•
A structural break where differential
movement has occurred along a
surface or zone of failure;
characterized by polished surfaces,
striations, slickensides, gouge,
breccia,
mylonite,
or
any
combination of these
•
Shear zones are localized zones of
mainly ductile deformation within
rocks at scales of between
millimetres and kilometres across
Slide 19
Slickensides
•
A fracture surface that is covered
with slickenlines – streaks of
fibrous quartz, calcite, etc.
•
The direction of the slicks
indicates the slip path on the fault
plane and the steps may help
determine the fault’s sense of slip
Branca (Albergaria-a-Nova), Portugal
Slide 20
Texture of rocks
• Texture - refers to the sizes and shapes of grains, the
relationships between neighboring grains, and the orientation
of grains within a rock.
• The characteristics related to grain size are known as a rock's
texture:
 Coarse-grained, fine-grained, and glassy are all descriptions
of a rock's texture.
Texture of igneous rocks can be analyzed to understand how the
rock became solid or crystallized from liquid, melted rock.
Slide 1
Relationships between
neighboring grains
Slide 2
Grain orientation
Slide 3
Crystalline rocks:
grain size
Slide 4
Crystalline rocks:
grain size uniformity
Slide 5
Clastic rocks:
grain size
Slide 6
Clastic rocks:
grain size uniformity
Slide 7
Clastic rocks:
grain shape
Slide 8
Igneous rocks texture
• Phaneritic texture: comprised of large crystals that are
clearly visible to the eye with or without a hand lens or
binocular microscope.
Slide 9
Igneous rocks texture
• Aphanitic texture: small crystals that cannot be seen by
the eye with or hand lens.
Slide 10
Igneous rocks texture
• Porphyritic rocks: composed of at least two minerals
having a conspicuous (large) difference in grain size.
Slide 11
Igneous rocks texture
• Glassy texture: the rock contains no mineral grains.
Slide 12
Igneous rocks texture
• Vesicle texture: presents holes, pores, or cavities within
the rock as the result of gas expansion (bubbles), which
often occurs during volcanic eruptions.
Slide 13
Igneous rocks texture
• Fragmental texture: pyroclastic rocks, that blown out into
the atmosphere during violent volcanic eruptions.
Numerous grains or fragments that have been welded
together by the heat of volcanic eruption.
Slide 14
Foliation and Lineation
Foliation surface
(plane)
Lineation direction
(line)
Foliation
Lineation
Gneiss
Quartzite
Metavolcanic rock
Slide 15
Foliated textures in
Metamorphic rocks
• Slaty texture - texture is caused by the parallel orientation
of microscopic grains. The rock is characterized by a
tendency to separate along parallel planes.
Slide 16
Foliated textures in
Metamorphic rocks
• Phyllitic texture - formed by the parallel arrangement of
platy minerals, usually micas, that are barely macroscopic
(visible to the naked eye).
Slide 17
Foliated textures in
Metamorphic rocks
• Schistose texture: resultes from the suhparallel to
parallel orientation of platy minerals such as chlorite or
micas. Other common minerals present are quartz and
amphiholes.
Slide 18
Foliated textures in
Metamorphic rocks
• Gneissic texture: coarse foliated texture in which the
minerals have been segregated into discontinuous hands,
each of which is dominated by one or two minerals.
Slide 19
NonFoliated textures in
Metamorphic rocks
• NonFoliated textures : are rocks with no visible preferred
orientation of mineral grains have. These rocks commonly
contain equidimensional grains of a single mineral such as
quartz, calcite, or dolomite.
• Examples of such rocks are quartzite , formed from a
quartz sandstone, and marble , formed from a
limestone or dolomite.
Slide 20
Water content
• Water content or moisture content is the quantity of water
contained in a rock on a volumetric or gravimetric basis.
Slide 1
Weathering
• Weathering is the decomposition of Earth's rocks, soils and
minerals through direct contact with the planet's atmosphere. The
process of chemical weathering generally occurs in the soil and
rocks where water and minerals are in constant contact. Agents of
weathering are oxygen, air pollution, water, carbonic acid, and
strong acids.
•
Two important classifications of weathering processes exist — physical and
chemical weathering.
 Mechanical or physical weathering involves the breakdown of rocks
and soils through direct contact with atmospheric conditions, such as
heat, water, ice and pressure.
 The second classification, chemical weathering, involves the direct
effect of atmospheric chemicals or biologically produced chemicals
(also known as biological weathering) in the breakdown of rocks,
soils and minerals.
Slide 1
Weathering
Weathering occurs in situ, or "with no movement", and thus should
not be confused with erosion, which involves the movement of rocks
and minerals by agents such as water, ice, wind and gravity.
Water has preferentially gained
access to the large fractures
running from upper left to lower
right and has weathered these
areas faster than the rock face.
Slide 2
Weathering of granitic rocks
• Ferro-magnesian minerals decay first, followed
by feldspars
• Quartz is extremely stable, and remains
unaltered
• This is why quartz beach and channel sands
are such common residual weathering products
Slide 3
Susceptibility to weathering
Susceptibility
to weathering
is proportionate
to chemical
exchange with
oxygenated
groundwater
Slide 4
Ref: http://www.geolsoc.org.uk/
Slide 1
Earth and rock cycle
eBook:
Understanding Earth, by John Grotzinger, Thomas H. Jordan,
Frank Press and Raymond Siever, 6th edition,
in http://www.whfreeman.com/understandingearth/
Slide 2
Metamorphic rocks
• Metamorphic rocks are rocks that have "morphed" into another
kind of rock. These rocks were once igneous or sedimentary rocks.
• Rocks are under tons and tons of pressure, intense heat,
geological time and fluids, which fosters heat build up, and this
causes them to change.
• They may be formed simply by being deep beneath the Earth's
surface, subjected to high temperatures and the great pressure of
the rock layers above it.
• They can form from tectonic processes such as continental
collisions, which cause horizontal pressure, friction and distortion.
• They are also formed when rock is heated up by the intrusion of
hot molten rock called magma from the Earth's interior.
Slide 1
Slide 2
Metamorphic rocks
• Metamorphic rocks can be:
 Foliate or
 Non-foliate.
• The layering within metamorphic rocks is called foliation (derived
from the Latin word folia, meaning "leaves"). It occurs when a rock
is being shortened along one axis during recrystallization. This
causes the platy or elongated crystals of minerals, such as mica
and chlorite, to become rotated such that their long axes are
perpendicular to the orientation of shortening. This results in a
banded, or foliated, rock, with the bands showing the colors of the
minerals that formed them.
• The planar fabric of a foliation typically forms at right angles to the
minimum principal strain direction.
• Foliation may parallel original sedimentary bedding, but more often
is oriented at some angle to it.
Slide 3
Classification of
metamorphic rocks
• Metamorphic rocks make up a large part of the Earth's
crust and are classified by texture and by chemical
and mineral assemblage (metamorphic facies).
•
These minerals, known as index minerals, include sillimanite,
kyanite, andalusite and some garnet.
• Other minerals, such as olivines, pyroxenes, amphiboles, micas,
feldspars, and quartz, may be found in metamorphic rocks, but
are not necessarily the result of the process of metamorphism.
Slide 4
Metamorphic rocks
Quartzite
Marble
5
Metamorphic rocks
Gneiss (with a gneissic texture)
Quartzite (non-foliated)
6
Sedimentary rocks
• Sedimentary rock is the type of rock that is formed by
sedimentation of material at the Earth's surface and within bodies of
water.
• Sedimentation is the collective name for processes that cause
mineral and/or organic particles (detritus) to settle and accumulate
or minerals to precipitate from a solution.
• Before being deposited, sediment was formed by weathering and
erosion in a source area, and then transported to the place of
deposition by water, wind, mass movement or glaciers.
• Sedimentary rocks appear in layer forms, forming thick deposits on
land or on the sea floor. These layers are horizontal, tilted, folded or
faulted. Sedimentary rocks often occur in shallow parts of the sea or in lakes in
desert areas where evaporation is higher than precipitation. As evaporation
takes place, water is lost and the dissolved minerals form crystals.
Slide 1
Sedimentary rocks
• The sedimentary rock cover of the continents of the Earth's crust is
extensive, but the total contribution of sedimentary rocks is
estimated to be only 5% of the total volume of the crust.
• Sedimentary rocks are only a thin veneer over a crust consisting
mainly of igneous and metamorphic rocks.
Slide 2
Classification of
sedimentary rocks
• Sedimentary rocks are classified into three groups. These groups
are:
 Clastic,
 Chemical precipitate and
 Biochemical (or biogenic).
Slide 3
Classification of
clastic sedimentary rocks
Particle grain
size (mm)
Sediments
Rocks
>2
Gravel
Conglomerate
0,0062-2
Sand
Sandstone
0,0039-0,0062
Silt
Siltstone
<0,0039
Clay
Mudstone
Slide 4
Classification of
biochemical and chemical sediments
and sedimentary rocks
Origin of sediments
Rocks
Chemical composition
Minerals
Limestone
Calcium carbonate
(CaCo3)
Calcite (aragonite)
Chert
Silica (SiO2)
Opal, chalcedony,
quartz
Organics
Carbon Compounds
Carbon compounded with
oxygen e hydrogen
(coil), (oil), (gas)
No primary sediment
(formed by diagenesis)
Dolostone
Calcium-magnesium
carbonate (CaMg[CO3]2)
Dolomite
Iron
Oxide sediment
Iron formation
Iron silicate; oxide
(Fe2O3), carbonate
Hematite, limonite e
siderite
Evaporite
Sodium chloride (NaCl);
calcium sulphate (CaSO4)
Gypsum, anhydrite,
halite, others salts
BIOCHEMICAL
Sand and mud
(primarily bioclastic)
Siliceous sediment
Peat, organic matter
CHEMICAL
Evaporite sediment
Press, Frank et al. (2003) - Understanding Earth, Freeman & co 4th
edition
Slide
5
Colour of sedimentary rocks
• The colour of a sedimentary rock is often mostly determined by iron,
an element which has two major oxides:


iron(II) oxide and
iron(III) oxide.
• Iron(II) oxide only forms under anoxic circumstances and gives the
rock a grey or greenish colour.
• Iron(III) oxide is often in the form of the mineral hematite and gives
the rock a reddish to brownish colour.
Slide 6
Sedimentary rocks
Evaporites
Sandstone
Limestone
7