Guided Notes on Identifying Minerals Chapter 4, Section 2.

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  • Guided Notes on Identifying MineralsChapter 4, Section 2

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

  • ColorWhat causes it? the presence of trace elements

    How reliable is it? It is one of the least reliable clues to a minerals identity.

  • LusterDefinition: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

  • Texture

    Definition: how a mineral feels to the touch

    Examples: fluorite has a smooth texture, talc has a greasy texture

  • StreakDefinition: the color of a mineral when powdered

    How useful is it? It is one of the most reliable clues to a minerals identity

    What are its limitations? It only works on minerals that are softer than porcelain

  • HardnessDefinition: how easily a mineral can be scratched

    What causes it? Hardness is caused by the arrangement of a minerals atoms

    How reliable is it? Hardness is one of the most reliable clues to a minerals identity

  • CleavageDefinition: 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

  • FractureDefinition: breaking unevenly with rough edges

    What causes it? Tightly bonded atoms

    Examples: quartz has irregular fracture, flint has conchoidal fracture

  • DensityDefinition: 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)

  • Double RefractionDefinition: 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

  • MagnetismWhich mineral exhibits it? magnetite

  • Describe how the Mohs scale of hardness is usedAny mineral with a greater hardness than other mineral will scratch the softer mineralThe Mohs scale places common minerals in order of hardness, ranging from 1 to 10

  • Describe how scientists use specific gravitySpecific 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

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

  • 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.

  • 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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