Guided Notes on Identifying Minerals Chapter 4, Section 2

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

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.

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

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

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

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

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

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

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)

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

Magnetism Which mineral exhibits it? magnetite

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

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

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