AMIIT SONI
(LABORATORY DIRECTOR, IGTLJ)
http://www.igtlj.com/
Precious: Has beauty,
durability, size, and rarity.
(Diamond, emerald,
opal,ruby,safphire)
Semi-precious: only two of
those (quartz, Jade)
A gemstone or gem (also called a
precious or semi-precious stone) is
a piece of attractive mineral, which
when cut and polished is used to
make jewelry or other decorations.
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The Mohs Scale characterizes
the scratch resistance of
different types of minerals
through the ability of a harder
material to scratch a softer
material. It was created in
1812 by the German
mineralogist Friedrich Mohs.
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Most gemstones are hard, but some soft
minerals are used in jewelry because of
their luster or other physical properties
that have value.
Luster: the way light interacts with the
surface of a crystal, rock, or
mineral.Sheen.
Greasy Luster
Greasy minerals resemble fat
or grease. A greasy lustre
often occurs in minerals
containing a lot of
microscopic inclusions. Some
examples are opal and
cordierite.Many minerals with
a greasy lustre also feel
greasy or smooth.
Metallic Luster
Metallic minerals have
the lustre of polished
metal.
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Adamantine Luster
Adamantine minerals have the
best lustre. It is mostly seen
in diamond.Diamond minerals
are transparent and refract
the light the best.Minerals
with a true adamantine lustre
are uncommon.
Dull Luster
Dull (or earthy) minerals have
little to no lustre, because they
are coarse and grainy, which
scatters light in all directions
instead of reflecting it. These
minerals are not used for
jewlery or decorations.
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Submetalic Luster
Submetallic minerals have similar
lustre to metal, but are duller and less
reflective
Vitreous Luster
Vitreous minerals have the lustre of
glass. This type of lustre is one of the
most commonly seen, and occurs in
transparent or translucent minerals
minerals have
a luster
resembling
wax.
Waxy luster
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Pearly Luster
Pearly minerals consist of thin
transparent sheets. Light reflecting
from these layers give them a lustre
similar to Pearls.
Resinous Luster
Resinous minerals have
the appearance of chewing
gum chewing or plastic
Silky Luster
Silky minerals have a parallel
arrangement of fine fibers. This
makes the minerals look like silk.
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Magmatic Crystallization:
Cooling Magma produces crystals of different kinds of minerals. Crystals
are formed from the lava when the volcano erupts. Examples: moonstone,
topaz and corundum.
Metamorphic deposits:
When a rock is in a high
temperature and or high
pressure, the chemical
components get
rearranged into new
minerals. Gem minerals
formed are diopside,
corundum, andalusite,
sillimanite, kyanite,
epidote, and garnet.
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Metamorphic deposits:
When a rock is in a high temperature and or
high pressure, the chemical components get
rearranged into new minerals. Gem minerals
formed are diopside, corundum, andalusite,
sillimanite, kyanite, epidote, and garnet.
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http://en.wikipedia.org/wiki/Gemstone
http://en.wikipedia.org/wiki/Lustre_(mineralogy)
http://www.gemstonebuzz.com/gemstone-formation
http://images.google.com/imgres?
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www.eoearth.org/article/Mohs,_Frederick&usg=__wRdbD8V99xE1XCIAy_h-
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http://www.okaloosa.k12.fl.us/technology/WOWLessons/WOWResources/RockCycleDiagram.gif
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Gem Testing Laboratory in India