Gemstones

Gemstones, or gems, are minerals that human beings consider especially attractive and use to make jewelry.

A gemstone's transparency, brilliance and hardness depend upon the particular atomic arrangement of its crystals.

Every continent on Earth contains in its rock the raw crystals of at least some gemstones.

Although South Africa is famous for its diamond mines, diamonds are also found in Canada, India, Russia, Brazil and Australia.

Emeralds are mined chiefly in Peru, Colombia, South Africa and Russia.

Many rubies are obtained in Burma, while sapphires mostly come from Australia and Asia.

Most types of gemstones can be found in special geological formations called pegmatites, which originate from molten rock magma rising inside the Earth.

The magma contains acidic solutions of minerals that move upward through fissures in rock in the Earth's crust.

As these solutions cool, their dissolved minerals precipitate as crystals.

Diamonds are not found in pegmatites. Instead, they can be found deep within the Earth, where they remain under intense heat and pressure.

Diamonds are made up of carbon atoms packed in tight crystal structures. Their hardness and sheen are both results of the carbon's crystal structure.

A sapphire's starlike gleam - its asterism - is caused by an intersecting pattern of gas bubbles trapped within the crystal dur-ing its formation.

Rubies and sapphires are chemically identical. Both types of gems are both made up of combinations of oxygen and aluminum. They owe their different colors to small traces of impurities. The blood red of the ruby comes from chromium atoms. The deep blue of the sapphire comes from iron and titanium.

Emeralds consist of oxygen, silicon, aluminum and beryllium. Their green shades come from titanium and chromium atoms present as impurities.