Minerals

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Mineral DefinitionMost Abundant ElementsClassification of MineralsMineral Identification

Mineral

A Naturally Occurring

Inorganic Solid

with a Definite Chemical

Composition

and Crystalline Structure.

A. Naturally occurring

A mineral has to be found on the earth's surface or dug up out of the crust, not made in a lab somewhere by people.

Examples of man- made objects are bricks, cement, and glass

B. Inorganic

This means that they do not come from living things. 

 

Since coal forms naturally in the crust

and from living things it is not a mineral

C. SolidSolids are

substances that have a definite shape and a definite volume.

The particles are tightly packed and can not flow freely.

D. Crystal structure

The atoms that minerals are made of are connected to each other in a pattern. 

This pattern is called its crystal structure.

The flat sides form faces

E. Definite Chemical CompositionThis means that there

is a specific chemical formula for each mineral. 

The mineral pyrite is made of 1 atom of iron for every 2 atoms of sulfur. (FeS2)

Pyrite will have the same chemical formula regardless of where it is found.

How Minerals FormCrystals from Magma

• Magma cools = atoms bunch together/combine

• Cools fast = small crystals• Cools slowly = larger crystals

Crystals from Solution• Water evaporates (leaving behind ions that form into crystals)

• Halite

How do minerals form?In general minerals can form in two

ways: through crystallization of melted materials, and through crystallization of materials dissolved in water.

Magma that cools at a slow rate will produce large crystals while magma or lava that cools rapidly will produce small crystals.

Most Abundant Elements in the Earth’s Crust

Sodium 3%

Aluminum8%

Silicon27%

Oxygen46%

Iron5%

Potassium 3%Magnesium

2%Other2%

Calcium 4%

Silicates (SiO4)

Quartz (SiO2)

Agate - Onyx (SiO2)

Amethyst (SiO2)

Beryl - Aquamarine (Be3Al2(SiO3)6

Chalcedony (SiO2)

Orthoclase (K, Al Si3O8)

Plagioclase (Na, Ca, Al3SiO4)

Nepheline (Na, Ca, AlSiO2)

Muscovite - mica (K, Al3 Si3O10)

Biotite - mica (K, (Mg, Fe)3 Al3SiO10)

Olivine (Mg Fe)2 SiO4)

Pyroxene (Mg, Fe)2, Ca, Al SiO4)

Amphibole - Hornblende (Mg, Fe Ca Al SiO4)

Garnet (Mn, Mg, Fe, Ca, SiO4 )

Talc (Mg3Si4O10)

Carbonates (CO3)Calcite (CaCO3)

Dolomite (Ca, Mg, CO3)

Siderite (FeCO3)

Cerussite (PbCO3)

Malachite (CuCO3)

Sulfates (SO4)

Gypsum (CaSO4)• alabaster• satin spar• selenite

Halides

Halite (NaCl)Fluorite (CaF2)

Iron Oxides FeOMagnetite (Fe3O4)

Hematite (Fe2O3)

Goethite (HFeO2)

Chromite (FeCr2O4)

Limonite (2 FeO)

Sulfides SPyrite (FeS)Galena (PbS)

OxidesCorundum (Al2O3)

Phosphates (PO4)Apatite Ca5(OH, F, Cl)(PO4)3

Native ElementsGold AuSilver AgCopper CuSulfur SGraphite CDiamond C

Mineral Identification

Identifying

Minerals

Each mineral has its own

characteristics or properties

that help you identify it.

The Physical Properties of Minerals• Hardness• Color• Streak• Luster• Fracture• Cleavage• Specific Gravity• Other – magnetic, smell, taste, acid

Mohs Scale

1824, Freidrich Mohs

Mohs Scale of Hardness1 Talc2 Gypsum3 Calcite4 Fluorite5 Apatite6 Orthoclase (Feldspar)7 Quartz8 Topaz (Beryl)9 Corundum10 Diamond

Moh’s Scale of Hardness

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Hardness #1Talc - talc has perfect cleavage in one direction. This means that this mineral breaks into thin sheets. As a result, it feels greasy to the touch (which is why talc is used as a lubricant).

Hardness #2Fingernail 2.5

Gypsum

Shape: Monoclinic (often forms thick tabular or prism shaped

crystals)

Luster: Pearly

Color: White, yellowish, or brown

Streak: White

Hardness: 2 on Mohs Hardness Scale

Cleavage: Perfect in one direction, poor in another direction

Fracture: Thin elongate fractures

Hardness #3Piece of copper (2.5-3)

Calcite

Shape: Trigonal (rhombahedral shape) Luster: Glassy to resinous. Large samples often look dull. Color: Usually white or colorless but sometimes is found in light pastel colors. Streak: White Hardness: 2.5 to 3Cleavage: Perfect in three directions Fracture: Conchoidal

Everyone's favorite way of identifying calcite is the acid test. When you place a drop of

weak acid, such as vinegar, on calcite, it will bubble. This happens because a reaction

causes a little bit of the calcite to break down, releasing carbon dioxide gas, making the

bubbles.

Hardness #4Iron nail 4.5

Fluorite

Hardness #5

Glass 5.5

Apatite

Hardness #6

Feldspar

Shape: Monoclinic (Flat tabular or prism-shaped crystals) Luster: Glassy or pearly Color: Cream to pink Streak: White Hardness: 6Cleavage: Yes Fracture: Conchoidal or brittle

Hardness #7

QuartzShape: Trigonal (Perfect crystals are usually 6-sided prisms with a pyramid shape at the end. However, it is much more common to find many crystals that have grown in a mass or broken crystals.) Luster: Glassy or greasy Color: Colorless or white. Some varieties are pink or smoky. Streak: White Hardness: 7 on Mohs Hardness Scale Cleavage: None

Hardness #7

QuartzThese three crystals of the mineral quartz show how the same type of mineral can have different colors! The pink sample is called rose quartz and the dark sample is called smoky quartz. Notice how these samples do not look like crystal shapes because they have fractured. Windows to the Universe

Hardness #8

Hardness #9

Corundum

Hardness #10

Luster

Descriptions of Luster• Metallic• Glassy• Earthy• Dull• Waxy• Vitreous (clear)• Silky• Pearly• Resinous (plastic)• Sub-metallic• Greasy

Specific GravityRatio of weight of the mineral when compared to the same volume of water.

Streak• The color of a mineral when it is in

powder form• Mineral must be softer than streak

plate

Cleavage and Fracture• The way a mineral breaks

• Cleavage – mineral can be broken along smooth, flat plains

• Fracture – minerals that break with uneven, rough, or jagged surfaces

Other Properties• Magnetic

• Acid Test

• Double image