Mineral IdentificationMr. Jensen

Ref: McGuire – ES/PS

Identifying Minerals• Minerals can be

identified using their distinctive physical and chemical properties.

• Mineral properties include:– Color – Luster– Hardness– Cleavage– Streak– Characteristics– Composition

Table 2-1: Common

Rock Forming Minerals

Minerals: Color• Color

– Many minerals have a characteristic color

– Impurities may discolor certain light colored minerals• Ex. Quartz and calcite

which are typically colorless.

– Dark color minerals typically do not have this problem.

Minerals: Luster• Luster

– Describes the way light is reflected from the freshly cut surface of a mineral.

– Metallic Luster• Hard shiny look like polished metal.• Light is unable to penetrate.• Ex. Pyrite, galena and magnetite

– Non-Metallic Luster• May be shiny but some light is able to penetrate.• Includes glassy, waxy, pearly and earthy (dull)

lusters• Ex. Calcite, quartz and feldspar

Minerals: Streak• Streak

– The color of the mineral in a powder form.

– The test for streak is performed by rubbing a fresh corner of the mineral across a white, unglazed streak plate.

– Several minerals have a streak that is not the same color as the mineral itself.• Most metallic luster minerals

have a dark colored streak. (Ex. Graphite, Pyrite)

Minerals: Crystal Structure

• Crystal Structure– Minerals form

characteristically shaped crystals

– A crystal is a regularly shaped solid formed by an ordered pattern of atoms.

Minerals: Hardness• Hardness

– Minerals differ in hardness– Tested by scratching mineral with other materials of known

hardness– Friedrich Mohs (Geologist) created the Moh’s scale for

hardness

Minerals: Cleavage• Cleavage

– If a mineral breaks readily along flat surfaces it shows cleavage

– Many minerals break along flat surfaces called cleavage planes

– Minerals that break along even surfaces that do not follow atomic arrangement (crystal faces) are said to show fracture

Minerals: Density• Density

– Minerals vary in density and specific gravity (ratio of density and water)