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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)
Iron Oxides FeOMagnetite (Fe3O4)
Hematite (Fe2O3)
Goethite (HFeO2)
Chromite (FeCr2O4)
Limonite (2 FeO)
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 of Hardness1 Talc2 Gypsum3 Calcite4 Fluorite5 Apatite6 Orthoclase (Feldspar)7 Quartz8 Topaz (Beryl)9 Corundum10 Diamond
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).
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
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.
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
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
Descriptions of Luster• Metallic• Glassy• Earthy• Dull• Waxy• Vitreous (clear)• Silky• Pearly• Resinous (plastic)• Sub-metallic• Greasy
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
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