The Mineral Diamond

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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