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Minerals and Resources
Minerals Versus Rocks
Mineral - any naturally formed, solid chemical element or compound
that has a definite composition and crystalline structure
Rock - any natural, solid aggregate material, usually made of minerals
All minerals are rocks, but not all rocks are made of minerals
Quartz
Granite
Mineral Properties
•Chemical composition
•Crystalline shape
•Hardness
•Color
•Streak
•Luster
•Cleavage
•Fracture
•Specific Gravity
•Magnetism
These properties are used to
identify different minerals
Chemical Composition
Extremely important for the minerals
industry. Often want an element or
compound in mineral, and not necessarily
the mineral itself
Ex.: iron and sulfur from iron pyrite (FeS2)
Identifying a mineral by chemical composition requires
submitting a sample for chemical analysis; can be time consuming
and expensive
Crystalline Shape
Useful for identification; of little use for industry, as crystalline
shape can be replicated in lab
Shape normally determined by chemical formula
Jewelry about the only use for
this property; even then, the fact
that crystals can be artificially
created means that their value is
artificial, as well
Hope Diamond
Hardness
Mho’s Scale
1 = Talc
2 = Gypsum
3 = Calcite
4 = Fluorite
5 = Apatite
6 = Orthoclase
7 = Quartz
8 = Topaz
9 = Corundum
10 = Diamond
Relative scale based upon what
mineral will scratch what mineral
Ex. Orthoclase will scratch apatite,
but quartz will scratch orthoclase
Fingernail is about a 2.5; steel nail = 5.5
Diamond is hardest, which means that it
does have some industrial application
Hardness does not relate to elemental scarcity or value
Color and Streak
Color - what color unmolested mineral appears to be
Streak - color of ground mineral
These two can be radically different.
Ex.: Iron pyrite color is gold (fool’s gold);
streak is black
Hematite is black/gray; streak is red-brown
Color is unreliable as identifier since impurities can change it;
streak is more reliable
Other Properties
Depending upon mineral, will use a variety of other identifiers
Magnetism - used to identify iron ores
Cleavage - used to identify minerals like mica and gypsum that
form crystals that loosely bond together
Fracture - helps to identify minerals with crystalline shapes that
do not cleave
Mineral Types
Based upon the key elements in the chemical composition,
minerals are grouped into subcategories
•Silicates (feldspars, garnets, micas, olivine, quartz, clay minerals)
•Native Elements (diamond, sulfur, gold)
•Sulfides (galena, pyrite, millerite, sphalerite)
•Sulfates (barite, celestite, gypsum, secondary sulfates)
•Oxides (goethite, hematite, ilmenite, limonite, uranium minerals)
•Carbonates (calcite, dolomite, other iron-carbonate and others)
•Phosphates (apatite, vivianite, pyromorphite)
•Halides (fluorite, halite)
Silicates
The largest group of minerals (30% of all minerals; 90% of whole
crust); defined by having SiO4 tetrahedra
Includes some gemstones such as tourmaline and topaz
Also has useful minerals such as talc, kaolin, and mica
Rocks made from silicates very useful for road and building
materials
Native Elements
Contains all of the metals (gold, silver, copper, etc.) and
metal alloys
Also includes diamonds and graphite (carbon)
Rare to find elements in their natural state; oftentimes, a
primary method of metal extractions is from some other
class
Ex. Copper and lead from sulfide minerals
Strategic Resources
Defn. - resources that a country uses, but cannot produce enough
to meet demand
If cannot guarantee supply, economy could be hurt if supplies
cut; Ex. OPEC oil embargo of 1973
Wealthy nations try to stockpile surplus to act as buffer against
outside forces affecting economy
Mining
Hollywood image of old man
with mule, pick axe, and
dynamite all but disappeared
Vulcan Materials pit mine, Kennesaw, GA, 1993
Most economic mining done
on huge scale with big
equipment
•Open pit - dig deep into the ground, exposing new rock to surface
•Stripmining - shallow mine over large area
•Underground mining - tunnels
Open Pit
Mineral ore dug from deep hole
created in the surface.
Walls of pit have roads built into
them for cranes, trucks, etc. to
be able to get to bottom
Economics of recovery have to constantly be re-evaluated, as hole
must get wider as go deeper (walls are the road system)
Stripmine
Differs from open pit in horizontal extant
Stripmines are going after near horizontal
seam of materials that are near the surface
Overburden is stripped from seam, and
then mineral is extracted
Once mineral removed, overburden put
back on top
Federal law now requires remediation
Underground Mining
Pickaxe and dynamite have
been replaced by large
tunneling equipment that does
the job safer and faster
Must leave some pillars of
material behind, lest a cave-in
ensue
Most dangerous form of mining
Miner safety in jeopardy from cave-ins and dust (black lung
disease)
Other Techniques
Hydraulic mining - sediments are blasted from hillside with water
jets; sediment is sent through sluice boxes; not done much in U.S.,
but is done many other places (South America)
Dredging - similar to hydraulic mining,
with the exception being that
the sediment is scooped out of the
ground instead of being blasted
out with water
Mining Pollution
•Water passing through mine leaches toxic chemicals
•Tailings piles and ponds erode and contain toxics
•Processing chemicals are toxic and sometimes released
•Land slumpage when cave-ins occur
•Underground fires can burn for decades
•Many mines are abandoned when economics fail
•Energy used for entire process is large
Pictures from Berkeley Pit in Butte Montana
Superfund Sites
Processing
Some rocks and minerals take very little processing
Ex: crushed rock for roads and construction material
Others take an incredible amount of energy and produce great
quantities of waste
Smelting - heating metal ores to extreme temperature to release
metal; gaseous vapors are toxic and often acidic
Leach extraction - pour acid or base on crushed piles of ore,
extract metal from leachate by electrolysis; crushed ore is left
to contaminate water supply when finished, with acid or base
still present
Recycling
•Besides saving environmental damage for extraction and
processing, can save huge quantities of energy
•Recycling aluminum saves 95%
•Recycling glass saves 25%
•Recycling steel saves between 60-75%
•Recycling plastic saves 33%
of the energy needed to make them from virgin materials
Recycling just one aluminum can will save enough energy to
run a 100W lightbulb for 20 hours