Download Identifying Minerals

Identifying Minerals
Minerals can be identified by their properties.
One or more properties may be needed to properly identify
most minerals.
MINERAL TESTS
1) Hardness Mohs Scale of Hardness.
1) Talc
2) Gypsum
3) Calcite
4) Fluorite
5) Apatite
6) Orthoclase
7) Quartz
8) Topaz
9) Corundum
10) Diamond
# 1 softest
# 10 Hardest
#3 can scratch 1 and 2
but not #4
Hardness is determined by scratching not toughness.
Diamond is the HARDEST substance and its prime use is as an
abrasive.
2) Color--- Many minerals can be identified by color. This is
not always reliable because there are so many variations in
mineral types. SULFER is always yellow.
3) Streak--- The color of a finely powered mineral is known
as streak. Although the color of a mineral may vary, its
steak does not and is therefore a good indicator of
mineral type.
Streak is tested for by rubbing a specimen
on a streak plate (porcelin).
4) Cleavage--- A mineral has cleavage if it breaks along definite
planes. Cleavage depends on crystal structure and takes
place parallel to atomic planes. EX---- Halite , Flourite.
4)
Fracture--- The way a mineral breaks when it does not
Follow cleavage planes, Examples, are glassy,
(conchoidal) hackly, splintery, and any other way that is
not a smooth surface
5) Luster----- the way a mineral looks in reflected light. Can
be described a glassy, oily, dull, earthy, metallic, pearly,
adamantine, sparkly.
6) Specific Gravity (Heft) --- a comparison of the density of a
mineral with the weight of water.
Ex--- density of water is 1 gram / cm3
Density of limestone is 2.67gm/cm3
Density of gold 19.3 gm/cm3
7) Magnetism---- Many minerals contain iron or nickel and
may be attracted by a magnet. Some are magnetized and will
attract iron EX—Magnetite.
8)Acid Test-- If a mineral has carbon and O2 in its
composition it will “ fizz” when weak hydrochloric acid is
dropped on the sample. CALCITE
LIMESTONE
CHALK
all contain CaCO3
MARBLE
and will fizz.
Mineral tests are used with a guide to help identify mineral
by a process of elimination. If a mineral does not fizz during
an acid test, then it could not be calcite. If a specimen could
be scratched by a fingernail, it could not be quartz.
All tests need not be used to identify all minerals, some are
obvious, like pyrites metallic luster, or magnetites
magnetism, or the hardness of diamond.