What Are Diamonds Made Of?
Diamonds are made of pure Carbon, set in a tight Diamond Lattice Formation. Graphite is also made from pure Carbon, but it's crystal structure is in a layered, planar structure, which makes it much less strong and makes it not transparent and beautiful for jewelry.
Diamonds are made deep in the earth's structure, where high temperatures and high pressures from the earth above force the chunks of pure Carbon into the tight structure that we know as diamonds. This can take millions of years and awesome amounts of pressure and heat.
Diamonds typically form at depths of between 70 and 120 miles in the Earth's crust. They are typically forced up with magma in volcanic explosions.
With recent technology advances, diamonds can be manufactured in high pressure, high temperature chambers. But due to the diamond market does not certify such diamonds as 'jewelry grade' so as to keep the diamond market protected by naturally occurring diamonds.
As you can see, the structure of a diamond is very tightly packed. Carbon can pack itself into such a tight molecular lattice due to the fact that Carbon naturally has 4 valence electrons. This allows each Carbon atom to molecularly bond in a perfect and tight cubic configuration.
It's this tight crystal structure that make diamonds the hardest naturally occurring substance on earth. This same structure is what gives diamonds their clarity and beauty.