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The Mineral & Gemstone Diamond

PHYSICAL PROPERTIES:
Chemistry: C
Composition: Elemental Carbon
Class: Native Elements
Subclass: Non Metallic
Group: Carbon
Crystal System: isometric; 4/m bar 3 2/m
Fracture: conchoidal
Hardness: 10
Specific Gravity: 3.5
Refractive Index: 2.4
Luster: adamantine to waxy
Streak: White
Cleavage: perfect in 4 directions which forms octahedrons
Color: colorless, yellows, browns, grays, pinks, blue, black, reddish, greenish
Transparency: transparent to translucent
Associated Minerals: limited to those found in the kimberlite parent rock which is an ultramafic igneous rock composed mostly of olivine.

COMPOSITION:

 

DISTINGUISHING CHARACTERISTICS:
It is well known that Diamond is the hardest substance found in nature. But did you know that Diamond is 4 times harder than Corundum? Corundum (sapphire and ruby) is the next hardest substance.

However diamond's one weakness is that it has four directions of cleavage (perfect cleavage). So if it receives a sharp blow in one of these directions it will cleave, or split. Well cut and mounted diamonds are generally placed in a way that will protect these points.

Diamond and Graphite are both polymorphs of Carbon. They are both made of carbon but have very different structures and properties.

Diamond is hard, Graphite is soft Graphite is the lead in your pencil. Diamond does not conduct electricity, Graphite is a good conductor of electricity. Diamond is the best known 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.

Now here's a surprise for you. All of your Diamonds are turning to pencil lead!! Here's how it goes. 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. Fortunately it is an extremely slow process.

 

ENVIRONMENT:
Diamonds are mostly found in alluvial deposits the harder and heavier diamonds have survived when the parent rock has weathered and been worn away. They are mined from the original rocks in South Africa and in Arkansas. They occur in a basic plutonic rock in cylindrical, more or less vertical, plugs known as "pipes" Sporadic diamonds found in the eastern United States, in California, and in glacial deposits in the North indicate that there may be other, still unrecognized, diamond-bearing formations.

CRYSTAL DESCRIPTION:
Most Diamond crystals are brilliant, often well-formed, octahedrons. Cubes usually dull; hexoctahedrons usually almost spherical, with curved faces. Also in balls with a radiating structure, known as ballas, and in black compact masses known as carbomado. Flat triangular crystals are usually twinned octahedra.

LOCALITIES:
USA, Canada, Russia, Australia, Africa, Angola, China, Brazil, India, Venezuela

USES:
Only about 20% of the diamonds found are suitable for gem use, the balance are used in industry for tools and dies, or crushed to a fine abrasive powder.

FACTS & HISTORY:
Americans buy approximately fifty percent of the world's diamond jewelry.

In 1947, Frances Gerety, a young copywriter on the De Beers account at N.W. Ayer in New York, came up with the famous slogan "A diamond is forever."

Diamonds were first mined in India over 4,000 years ago.