How to identify a mineral

How to Identify a Mineral


Mineral Identification
• We identify minerals so we can recognize
valuable resources (useful or beautiful).


Mineral Identification
• There are 7 tests performed on minerals
so they can be identified.


Test 1


Test 1
• Mineral Appearance: Color and
appearance are two clues used to identify
minerals.

Azurite can always
be identified by its
striking blue color.


Test 1
• However, this test is not enough to identify
most minerals.

Which one is gold and which one is iron pyrite (fool’s gold)?

Test 2


Test 2
• Hardness: the measure of how easily a
mineral can be scratched.

Talc can be scratched by a fingernail, diamonds cannot
be scratched by anything but another diamond.


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Test 2
• Hardness is measured using a Mohs scale.


Test 3


Test 3
• Luster: the way a mineral reflects light.


Test 3
• A mineral can be metallic or non-metallic,
such as glassy, dull, pearly, or silky.

Non-metallic, dull

Non-metallic, glassy

Metallic


Test 4


Test 4
• Specific Gravity: a mineral’s weight is
compared to the weight of an equal sized
amount (volume) of water.

Gold has a specific gravity of 19, iron pyrite is 5 (= 5 times heavier than water.)


Fake or real???


Test 5


Test 5
• Streak: the color a mineral leaves on a
porcelain tile.

Hematite (on left) looks gray, but leaves a reddish-brown streak. Iron pyrite
(on right) is gold colored, but leaves a greenish-black streak.

Test 6


Test 6
• Cleavage or Fracture: how a mineral
breaks.


Test 6
• Cleavage: the physical property of some
minerals that allows them to break along
smooth, flat surfaces.

Mica always cleaves in thin, flat sheets. Halite cleaves at 90
degree angles.


Test 6
• Fracture: the physical property of some
minerals that causes them to break with
uneven, rough, or jagged surfaces.


Test 7


Test 7
• Other properties: some minerals have

unique properties that allow them to be
easily identified.
Magnetite
will pick up
iron like a
magnet


Test 7

Calcite can
cause
double
images