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- H 2 O as ice in a glacier is a mineral, but water is not.
Definite Crystal Structure
Highly ordered atomic arrangement of atoms in regular geometric patterns
Apatite Feldspar Diamond Quartz
Minerals are crystals with a repeated inner structure.
Definite Chemical Formula
Minerals are expressed by a specific chemical formula.
Calcite (CaCO 3 )
Quartz (SiO 2 )
Pyrite (FeS 2 )
Minerals made of only one type of atom (element) are called native elements.
Types of minerals
Minerals are most commonly classified by chemical composition.
The 2 main groups are silicates and nonsilicates.
Minerals containing a combination of silicon (Si) and oxygen (O) (most common elements in the earth’s crust)
Silicate minerals comprise about 90% of the Earth’s crust.
Silicates minerals often contain other elements such as aluminum, iron, magnesium, and potassium.
Granite is a rock comprised of the minerals feldspar, biotite mica and quartz.
Feldspar minerals make up half of the Earth’s crust and is the main component of most of the rocks found on the Earth’s surface.
Feldspar contains Si, O, Al, K, Na, and Ca
soft and shiny minerals that separate easily into sheets
biotite is one variety of mica
silicon dioxide ( SiO 2 )
is the basic building block of many rocks
minerals that do not contain the combination of Si and O
some of these minerals are made up of C, O, F, and S
Classes of nonsilicates
Native elements are composed of only 1 element
About 20 exist including Au, Pt, C, Cu, S and Ag
contain the combinations of carbon and Oxygen in their chemical structure
calcite (CaCO 3 ) is an example
carbonates are used in cement, building stones and fireworks
form when atoms containing fluorine, chlorine, iodine, or bromine (halogens) combine with potassium or calcium
Halite (NaCl) is better known as rock salt
Fluorite can have many different colors
Halides are often used in making fertilizers
compounds formed when elements like aluminum or iron bond with oxygen
Corundum (Al 2 O 3 ) and Magnetite (Fe 3 O 4 ) are important oxides
Are used in abrasives and airplane parts
minerals containing sulfur and oxygen (SO 4 )
gypsum (CaSO 4 * 2H 2 O) is a common example
makes the white sand at White Sands National Monument in NM
sulfates are commonly used in cosmetics, toothpaste and paints
minerals containing one or more elements such as lead, iron, or nickel combines with sulfur
Galena (PbS) is a sulfide
Sulfides are used to make batteries, medicines and electronic parts
Composition of the Earth’s Crust
- Oxygen (O)
- Silicon (Si)
- Aluminum (Al)
- Iron (Fe)
- Calcium (Ca)
- Sodium (Na)
- Potassium (K)
- Magnesium (Mg)
Eight Elements that make up over 98% of Earth’s Crust
Where Do Minerals Come From? Magma Evaporation In general, minerals form in two ways: Cooling magma - Crystallization of melted materials From solution - Crystallization of materials dissolved in water At the surface Beneath the surface
Magma is molten material from the mantle that hardens to form rock.
Lava is magma that reaches the surface.
Minerals form as hot magma cools inside the crust, or as lava hardens on the surface.
When these liquids cool to the solid state, they form crystals.
Size of Crystals
Magma closer to the surface cools much faster, producing smaller crystals.
Slow cooling leads to the formation of large crystals.
When magma remains deep below the surface, it cools slowly over many thousands of years.
The chemical composition of the magma
The amount of gas the magma contains
The rate at which the magma cools
Depends of several factors:
Minerals from Hot Water Solutions
This can happen on the ocean floor when ocean water seeps down through cracks in the crust.
When a hot water solution begins to cool, the elements and compounds leave the solution and crystallize as minerals.
A solution is a mixture in which one substance dissolves in another.
Sometimes, the elements that form a mineral dissolve in hot water and form a solution.
Minerals formed by Evaporation
Minerals containing potassium
Several other useful minerals also from by the evaporation of seawater:
Minerals can also form when solutions evaporate. Example: salt from sea water
Minerals formed by Metamorphism
When rocks are put under extreme heat and pressure, the chemical composition of the rock can change, forming new minerals.
Examples: calcite, garnet, graphite, hematite, magnetite, mica and talc.
How Are Minerals Identified?
Cleavage and Fracture
Usually the first and most easily observed
- Some minerals are the same color as others - Some minerals can have many colors
Not a reliable way to identify a mineral
QUARTZ ROSE QUARTZ SMOKY QUARTZ
General appearance of a mineral surface in reflected light
Examples of luster
Greasy: resembles the way petroleum jelly or a greasy surface reflects light
Silky: resembles the way silk reflects light
Earthy: dull, may be rough or dusty
Adamantine: resembles the way a diamond shines
Vitreous: similar to glass
Resinous: resembles the way plastic reflects light
Pearly: resembles the way pearls shine
Pitchy – looks like tar
Fibrous – looks like fibers
Resistance to scratching by different items; “scratchability”
Mohs Hardness Scale is used to determine the hardness of minerals by comparing them to substances of known hardness:
< 2 fingernail
~ 5 Steel of a pocket knife
5.5 Window Glass
6.6 Steel of a file
7 Quartz crystal
Mohs Mineral Hardness Scale
Softest Hardest 1 2 3 4 5 6 7 8 9 10
The color of a finely powdered mineral
Determined by rubbing the mineral on a piece of unglazed porcelain (streak plate)
The amount of matter in a given space
Specific Gravity is the comparison of a substance’s density to the density of water
Minerals have a characteristic crystal shape resulting from the atomic packing of the atoms when the mineral is forming
Cleavage and Fracture
Cleavage is the tendency of a mineral to split or crack along parallel or flat planes
Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes.
Obsidian No Cleavage 1 Direction of Cleavage Conchoidal Fracture BIOTITE QUARTZ
Reaction to HCl (Calcite)
Double refractive - a thin, clear piece of calcite placed over an image will cause a double image
Radioactivity - minerals containing radium or uranium can be detected by a Geiger counter
Glowing under ultraviolet light (Fluorite)
Economic Importance of Minerals
Minerals are in many things we see and use everyday such as; bricks, glass, cement, plaster, iron, gold
Every American Requires 40,000 Pounds of New Minerals per Year
at this level of consumption the average newborn infant will need a lifetime supply of:
-795 lbs of lead (car batteries, electric components)
-757 lbs of zinc (to make brass, rubber, paints)
-1500lbs of copper (electrical motors, wirings
-3593 lbs aluminum (soda cans, aircraft)
-32,700 lbs of iron (kitchen utensils, automobiles, buildings)
-28,213 lbs of salt (cooking, detergents)
-1,238,101 lbs of stone, sand, gravel, cement (roads, homes, etc.)