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9 Cards in this Set
- Front
- Back
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Define "mineral" |
A naturally occurring solid, formed by geologic processes, that has a crystalline structure and a definable chemical composition. |
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Why is glass not a mineral? |
The atoms, ions, and molecules in glass are not ordered into a crystal lattice. |
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List several ways a mineral can form. |
1. Solidification of a melt. 2. Precipitation from a water solution. 3. Diffusion through a solid. 4. Metabolism of organisms. 5. Precipitation from a gas. |
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Why do some minerals occur as euhedral crystals, whereas others occur as anhedral grains? |
Euhedral crystals form when a mineral's growth is uninhibited so that it displays well-formed crystal faces. Anhedral grains are more common, and occur when the growth of a crystal is restricted in one or more directions. These do not have well-formed crystal faces. |
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What are some physical properties used to define a mineral? |
Color, streak, luster, hardness, specific gravity, crystal habit, and cleavage. |
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How do you distinguish cleavage surfaces from crystal faces on a mineral? How does each type of surface form? |
Cleavage planes can be repeated, whereas a crystal face is a single surface. Cleavage forms in directions where the bonds holding atoms together in the crystal are weaker. Crystal faces develop as a crystal grows, based on the geometry of its internal structure. |
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What is the prime characteristic that geologists use to classify minerals? |
They are grouped by chemical composition, particularly by anionic group. |
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On what basis do mineralogists organize silicate minerals into distinct groups? |
Silicate minerals are distinguished from each other by the ways in which the silicon-oxygen tetrahedra that constitute them are linked. |
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What is the relationship between the way in which silicon-oxygen tetrahedra bond in micas and the characteristic cleavage of micas? |
Mica has very weak bonds in one direction, but strong bonds in the other two, so it splits easily into parallel sheets. |
