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UNIT 2 MINERALS PART 2 full lectureStructure of mineralsComposition of magma or fluids from which the minerals form. Conditions like temperature and pressure under which the mineral forms.Minerals formed from the same elements in the same proportions can have very different internal structures, (ex)depending on pressure which packs atoms more dense.
• 1. Polymorphs- different minerals with the same chemical composition but differing structures.
• Graphite is a form of pure carbon.• Its crystal structure forms sheets • of carbon
Diamond is another form of pure carbon. It forms deep in the Earth at high pressures and it’s the hardest substance.It crystal structure is dense and compact.
• 2. Mineral Identification• Minerals are identified by their physical and
optical properties. Some properties are more diagnostic then others so a combination is used to determine the mineral.
• Properties: color, luster, hardness, streak, Crystal form, cleavage, fracture, reaction to acid, taste, smell, magnetization, optical properties, elasticity, and specific gravity.
• b. Luster appearance of light reflected from minerals. Eamples include metallic luster, nonmetallic luster, glassy luster, and resinous luster.
Anhedral crystals form when crystals don’t have room
to grow and bump into each other feldspar in an igneous rock
Irregular boundaries between crystals due to interference during growth
-group of silicate minerals that readily separate into fibers that are: thin, flexible, heat resistant, chemically inert
many uses
Asbestos
Asbestos
Cleavage: Tendency to break along preferred planes of weakness.
Cleavages represent directions of weaker bonding between atoms.
Carbonate minerals, like calcite, dissolve in acid and release carbon dioxide
“The Acid Test”
CO2 bubbles
HalidesHalite (Na, Cl: NaCl)-> common table salt
SulfatesGypsum (Ca,S,O,H: CaSO4-H2O)-> calcium sulfate + water, main ingredient of plaster & other building materials
OxidesHematite (Fe, O: Fe2O3)-> steel
Important Non-silicate Minerals
Carbonates
Calcite (Ca, C, O: CaCO3)Dolomite (Ca, Mg,C, O: CaMg(CO3)2
Found together in sedimentary rock limestone.
Main ingredient to cement, roads & building stones.
Important Non-silicate Minerals
Over 4000 minerals: only few dozen are abundant, making up most rocks of Earth’s crust => rock-forming minerals
Only 8 elements make up most of crust’s minerals & represent over 98% of the continental crust
The two most abundant elements:
Silicon (Si) Oxygen (O)
The Common Rock-forming Minerals
Average composition of the Earth’s crust.
Percent of elements by WEIGHT
Question: What minerals would you expect to be most abundant on Earth?
Earth’s CrustPrimarily Si & O followed in abundance by Fe, Mg, Ca, Na, K, etc.
Dark colored (mantle and oceanic crust)Olivine (Si, O, Fe, Mg)Pyroxene (Si, O, Fe, Mg, Ca)Amphibole (Si, O, Fe, Mg)
Light colored (crust, esp. continental crust)
Quartz (SiO2) - Hard, transparentFeldspar (Si, O, Al, K, Na, Ca) - Hard, white, gray, pink Clay (Mostly come from weathering feldspar) Calcite (CaCO3, shells) Limestone - Used for cement
The Common Rock-forming Minerals