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Chemistry
: C, Elemental
Carbon
Class: Native Elements
Subclass: Non-metallics
Group: Carbon
Uses: as a gemstone and abrasive.
Diamond
is the ultimate gemstone, having few weaknesses
and many strengths. It is well known that Diamond
is the hardest substance found in nature, but
few people realize that Diamond is four times
harder than the next hardest natural mineral,
corundum (sapphire and ruby). But even as hard
as it is, it is not impervious. Diamond has four
directions of cleavage, meaning that if it receives
a sharp blow in one of these directions it will
cleave, or split. A skilled diamond setter and/or
jeweler will prevent any of these directions from
being in a position to be struck while mounted
in a jewelry piece.
As
a gemstone, Diamond's single flaw (perfect cleavage)
is far outdistanced by the sum of its positive
qualities. It has a broad color range, high refraction,
high dispersion or fire, very low reactivity to
chemicals, rarity, and of course, extreme hardness
and durability. Diamond is the April Birthstone.
In terms of it's physical
properties, diamond is the ultimate mineral in
several ways:
Hardness: Diamond
is a perfect "10", defining the top
of the hardness scale.
Clarity: Diamond is transparent over a
larger range of wavelengths (from the ultraviolet
into the far infrared) than is any other solid
or liquid substance - nothing else even comes
close.
Thermal Conductivity: Diamond conducts
heat better than anything - five times better
than the second best element, Silver!
Melting Point: Diamond has the highest
melting point (3820 degrees Kelvin)!
Lattice Density: The atoms of Diamond are
packed closer together than are the atoms of any
other substance!
Diamond is a polymorph of
the element carbon. Graphite is another polymorph.
The two share the same chemistry, carbon, but
have very different structures and properties.
Diamond is hard, Graphite is soft (the "lead"
of a pencil). Diamond is an excellent electrical
insulator, Graphite is a good conductor of electricity.
Diamond is the ultimate abrasive, Graphite is
a very good lubricant. Diamond is transparent,
Graphite is opaque. Diamond crystallizes in the
Isometric system and graphite crystallizes in
the hexagonal system. Somewhat of a surprise is
that at surface temperatures and pressures, Graphite
is the stable form of carbon. In fact, all diamonds
at or near the surface of the Earth are currently
undergoing a transformation into Graphite. This
reaction, fortunately, is extremely slow.
PHYSICAL CHARACTERISTICS:
- Color is variable and
tends toward pale yellows, browns, grays, and
also white, blue, black, reddish, greenish and
colorless.
- Luster is adamantine
to waxy.
- Transparency crystals
are transparent to translucent in rough crystals.
- Crystal System is isometric;
4/m bar 3 2/m
- Crystal Habits include
isometric forms such as cubes and octahedrons,
twinning is also seen.
- Hardness is 10
- Specific Gravity is 3.5
(above average)
- Cleavage is perfect in
4 directions forming octahedrons.
- Fracture is conchoidal.
- Streak is white.
- Associated Minerals are
limited to those found in kimberlite rock, an
ultramafic igneous rock composed mostly of olivine.
- Other Characteristics:
refractive index is 2.4 ( very high), dispersion
is 0.044, fluorescent.
- Notable Occurrences include
South Africa and other localities throughout
Africa, India, Brazil, Russia, Australia, and
Arkansas.
- Best Field Indicator
is extreme hardness.
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