Mineral identification

Mineral Identification
Mr. Jensen
Ref: McGuire – ES/PS


Identifying Minerals
• Minerals can be
identified using their
distinctive physical
and chemical
properties.

• Mineral properties
include:
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–
–
–
–
–
–

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)