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Geology

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Minerals

minerals

Minerals Reading
To be considered a mineral, the substance in question must meet the following criteria:

• Naturally occurring
• Solid
• Inorganic
• Definite chemical composition
• Definite crystalline structure
How do we identify minerals?
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COLOR
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Most visible characteristic, but least reliable because many minerals share the same color and many minerals exist in different colors.
STREAK
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The color of the mineral in powdered form (use a “streak plate”).  Very reliable tool for identifying samples. Note: the color of the powdered form is often different from the color of the solid form.
 
FRACTURE/ CLEAVAGE
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Cleavage is the tendency of a mineral to split along one or more smooth, flat surfaces. If a mineral does not display cleavage, it is said to have fracture, which means it breaks unevenly.
HARDNESS
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The mineral’s resistance to being scratched. Minerals are compared to the ten minerals
on the “Moh’s Scale of Hardness”. Minerals are often compared to glass (hardness: 5.5)
LUSTER 
 
Either metallic (shiny, like a polished metal) or nonmetallic (dull, with no shine). Types of nonmetallic luster include glossy, pearly, greasy, etc.
OTHER CHARACTERISTICS
 
that can be tested include: magnetism, reaction with chemicals, taste, specific gravity, crystal form, fluorescence, optics.
Calcite reaction to acid
Rocks

rocks

Rocks Reading
Earth Interior

Earths Interior

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