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Guided Notes on Identifying Minerals

Discover simple tests used by geologists to identify minerals based on physical and chemical properties like color, luster, texture, streak, hardness, cleavage, fracture, density, and more. Learn about specific gravity and ore classification.

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Guided Notes on Identifying Minerals

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  1. Guided Notes on Identifying Minerals Chapter 4, Section 2

  2. To identify minerals, geologists rely on several relatively simple tests, which are based on a mineral’s physical and chemical properties.

  3. Color • What causes it? the presence of trace elements • How reliable is it? It is one of the least reliable clues to a mineral’s identity.

  4. Luster • Definition:the way that a mineral reflects light from its surface • Two types: metallic and nonmetallic • What causes it? Differences in the chemical composition of minerals cause different lusters

  5. Texture • Definition: how a mineral feels to the touch • Examples: fluorite has a smooth texture, talc has a greasy texture

  6. Streak • Definition: the color of a mineral when powdered • How useful is it? It is one of the most reliable clues to a mineral’s identity • What are its limitations? It only works on minerals that are softer than porcelain

  7. Hardness • Definition: how easily a mineral can be scratched • What causes it? Hardness is caused by the arrangement of a mineral’s atoms • How reliable is it? Hardness is one of the most reliable clues to a mineral’s identity

  8. Cleavage • Definition: when a mineral splits evenly along one or more flat planes • What causes it? Weak atomic bonds in one or more direction • Examples: mica has perfect cleavage, halite has cubic cleavage

  9. Fracture • Definition: breaking unevenly with rough edges • What causes it? Tightly bonded atoms • Examples: quartz has irregular fracture, flint has conchoidal fracture

  10. Density • Definition: mass per unit of volume • What causes it? Differences in atomic weight and structure • How is it expressed? A ratio of mass divided by volume (g/mL)

  11. Double Refraction • Definition: the refraction of a single ray of light into 2 images • What causes it? The arrangement of atoms in a mineral • Which minerals exhibit it? Calcite (Iceland Spar) and zircon

  12. Magnetism • Which mineral exhibits it? magnetite

  13. Describe how the Mohs scale of hardness is used… • Any mineral with a greater hardness than other mineral will scratch the softer mineral • The Mohs scale places common minerals in order of hardness, ranging from 1 to 10

  14. Describe how scientists use specific gravity… • Specific gravity is the ratio of the weight of a substance to the weight of an equal volume of water. • Specific gravity is used as a measure of density because it contains easily understood numbers for comparison

  15. A mineral is called an ore if it contains a useful substance that can be mined at a profit.

  16. Ores located deep inside the earth are removed by underground mining. Ores near the surface are obtained from open-pit mines. If the cost of removing waste material from a mine becomes higher than the value of the mineral, then the mineral is no longer considered an ore.

  17. Gems are valuable minerals prized for their rarity and beauty. The beautiful colors of gemstones are caused by the presence of trace elements.

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