Minerals

Menu Mineral Definition Most Abundant Elements Classification of Minerals Mineral 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. Solid Solids 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 Composition This 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. (FeS 2 ) Pyrite will have the same chemical formula regardless of where it is found.

How Minerals Form Crystals 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

Silicates (SiO 4 ) Quartz (SiO 2 ) Agate - Onyx (SiO 2 ) Amethyst (SiO 2 ) Beryl - Aquamarine (Be3Al 2 (SiO 3 ) 6 Chalcedony (SiO 2 ) Orthoclase (K, Al Si 3 O 8 ) Plagioclase (Na, Ca, Al 3 SiO 4 ) Nepheline (Na, Ca, AlSiO 2 )

Muscovite - mica (K, Al 3 Si 3 O 10 ) Biotite - mica (K, (Mg, Fe) 3 Al 3 SiO 10 ) Olivine (Mg Fe) 2 SiO 4 ) Pyroxene (Mg, Fe) 2, Ca, Al SiO 4 ) Amphibole - Hornblende (Mg, Fe Ca Al SiO 4 ) Garnet (Mn, Mg, Fe, Ca, SiO 4 ) Talc (Mg 3 Si 4 O 10 )

Carbonates (CO 3 ) Calcite (CaCO 3 ) Dolomite (Ca, Mg, CO 3 ) Siderite (FeCO 3 ) Cerussite (PbCO 3 ) Malachite (CuCO 3 )

Sulfates (SO 4 ) Gypsum (CaSO 4 ) alabaster satin spar selenite

Halides Halite (NaCl) Fluorite (CaF 2 )

Iron Oxides FeO Magnetite (Fe 3 O 4 ) Hematite (Fe 2 O 3 ) Goethite (HFeO 2 ) Chromite (FeCr 2 O 4 ) Limonite (2 FeO)

Sulfides S Pyrite (FeS) Galena (PbS)

Oxides Corundum (Al 2 O 3 )

Phosphates (PO 4 ) Apatite Ca 5 (OH, F, Cl)(PO 4 ) 3

Native Elements Gold Au Silver Ag Copper Cu Sulfur S Graphite C Diamond 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 Hardness 1 Talc 2 Gypsum 3 Calcite 4 Fluorite 5 Apatite 6 Orthoclase (Feldspar) 7 Quartz 8 Topaz (Beryl) 9 Corundum 10 Diamond

Moh’s Scale of Hardness Ticking Generally Continues From An Old Quartz Timex Calendar Display

Hardness #1 Talc - 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 #2 Fingernail 2.5

Gypsum Shape: Monoclinic (often forms thick tabular or prism shaped crystals)Monoclinic Luster: Pearly Color: White, yellowish, or brown Streak: White Hardness: 2 on Mohs Hardness ScaleMohs Hardness Scale Cleavage: Perfect in one direction, poor in another direction Fracture: Thin elongate fractures

Hardness #3 Piece of copper (2.5-3)

Calcite Shape: Trigonal (rhombahedral shape)Trigonal 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 3 Cleavage: 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 #4 Iron nail 4.5 Fluorite

Hardness #5 Glass 5.5 Apatite

Hardness #6

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

Hardness #7 Quartz Shape: 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.)Trigonal Luster: Glassy or greasy Color: Colorless or white. Some varieties are pink or smoky. Streak: White Hardness: 7 on Mohs Hardness ScaleMohs Hardness Scale Cleavage: None

Hardness #7

Quartz These 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 Gravity Ratio 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