Download Rocks and Minerals

Rocks and Minerals
Minerals – What are they?
• Inorganic solid
• Crystal structure
– Repeating atomic structure
• Definite composition
– Pure substance
– elements
Crystal structure
of a diamond
Mineral Formation
• Come from magma (molten
rock below ground)
– Slow cooling: large crystals
Mineral formation, con’t
• Fast cooling: tiny crystals
Mineral Formation, con’t
• Above ground: magma called lava
– May have no crystals if cools too fast
Mineral formation, con’t
• Crystals may form from dissolving out of liquid
Calcite caves
Salt caves
Mineral Properties- distinguishing characteristics
• Color
• Luster- how light is
reflected
– Metal/nonmetal
Mineral Properties, con’t
• Hardness – Mohs Scale
Mineral Properties, con’t
• Streak
Mineral Properties, con’t
• Density d=m/v
• Density = Mass/volume
• Compare pumice and
lead
• Crystal shape
Mineral properties, con’t
• Cleavage – tendency to split
along smooth surfaces
Calcite has three directions of
cleavage. The cleavage directions are
not at right angles to each other, like
salt, but are inclined. The resultant
shape produced by the cleavage of
calcite is called a rhombohedron
Mineral properties, con’t
• Fracture – tendency to split irregularly
Fracture is the tendency of a mineral to break along
curved surfaces without a definite shape. These minerals
do not have planes of weakness and break irregularly.
Special properties
• Magnetic – magnetite
• Taste - halite
Special properties, con’t
• Fluorescence – glows under UV light
Special Properties, con’t
• Phosphorescence –
continues to glow when
UV light is removed
Special Properties, con’t
• Smell – sulfur
• Fizzes – in response to
acid: Calcite
Special Properties, con’t
• Radioactive - uranium
uranite
Mining for Uranium
Metatorbernite contains uranium
uranite
Uses of minerals
• Ores- minerals that can be re removed from rock in
usable amounts
– Metals- may be hammered, pressed, conduct electricity
and heat
Pressed metals
hammered
Copper and
silver wire
Uses of minerals, con’t
• Non-metals – variety of uses: Sulfur:
medicines, matches fertilizer
Uses of Minerals, con’t
• Gemstones – precious and valuable
– Rubies, emeralds, diamonds, sapphires are
considered precious stones
– Semi-precious : garnet, topaz, onyx and others
What is a Rock?
• Composed of one or more minerals
• May contain natural substances that are not
minerals
Types of Rock – classified by how
they form
Igneous
Sedimentary
Metamorphic
Igneous
• Means fire – from molten rock inside the earth
– Classified by composition and texture
•
•
•
•
Glassy: obsidian
Granite
Fine-grained: basalt
Coarse-grained: granite
Porphyritic – both large and small grains in one rock
Obsidian
Basalt
Porphyritic
granite
Igneous, con’t
• Classified by where it formed
– Extrusive: formed from lava brought to the surface and
cooled quickly
– Intrusive: fomed in magma and cooled slowly (granite
• Also known as plutonic rock or plutons (after Pluto: God to
the Underworld)
Extrusive - Basalt
A glacial igneous boulder with intrusive
sheet dikes
Sedimentary rock – formed from particles that
have been carried or deposited by wind or water
Mesa Verde - Colorado
Zion National Park - Utah
5% of the
Earth’s
surface is
sedimentary
rock
Sedimentary, classification
– Classic rocks – formed
from fragments of existing
rocks
• Conglomerate – if over 1/3
is made of pebbles
cemented together
Sediment (A)
may someday
become a clastic
rock (B) if
compacted and
cemented
together.
Coarse-grained clastic rock with mostly
rounded clasts (conglomerate), Hopi
Buttes, Arizona
Sedimentary Rock, classification, Clastic con’t
• Sandstones – made of sand-sized grains
• Shale – made of particles smaller than sand
Oil Shale
Sandstone has stripes in it that show when
the layer was made. This is a lot like rings
in the trunk of a tree
Black Shale
Sedimentary classification, con’t
• Organic Rocks – made from organisms
– Example Limestone, chalk, coal
White cliffs of Dover, England
Sediment may have a biological or
chemical origin. Shell fragments such as
these are often found on beaches in
tropical regions
Coal
Sedimentary Rock classification, con’t
• Chemical Rocks- Formed when minerals dissolve
out of water-Rock salt and gypsum
The gypsum "cotton wool" is a rare
phenomenon. The fibrous form of gypsum
is called Anhydrite, meaning gypsum
without water
Gypsum flowers "grow" in profusion on the wall of the Puketiti Flower Cave
in New Zealand. They are rocks, not living plants, despite the flower-like
shape. They seem to grow and curve out of the wall, like toothpaste forced
out of a tube. Some say they come out of cracks in the wall,
Metamorphic Rock
• Formed when chemical reactions, extreme heat or
pressure change an existing rock form
• May begin with either sedimentary or igneous rock
Metamorphic classification – by texture
• Foliated –(Latin word for leaf) –
thin and flat, break in layers
– Example slate and gneiss (nice)
Kinked telephone book as an analogy for
how kink bands form: a highly layered
structure (phone book or foliated
metamorphic rock) is compressed from the
sides, resulting in kinking in order to
accommodate the shortening of the
pages/foliation.
Red Slate
Metamorphic classification – by texture con’t
• Unfoliated – won’t break in
layers
– Example: Marble or quartzite
Marble
Nodular gray marble
Dentritic Quartzite
Rock Cycle