Gemstones and precious metals are substances from the Earth that humans consider especially valuable.
Gemstones
Gemstones, or gems, are minerals thought to be unusually attractive because of their bright coloring and brilliance.
They are used in jewelry because of their beauty.
The way in which a gemstone’s crystals are arranged determine its hardness, brilliance and transparency.
Gemstone crystals are found in rocks all over the Earth.
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 geological formations known aspegmatites, which are formed when magma rises inside the Earth.
As the magma rises, solutions containing dissolved minerals move through fissures in the Earth’s crust.
When these solutions cool, the 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.
A diamond is made up of carbon atoms packed in tight crystal structures. This structure causes them to become very hard – diamonds are the hardest naturally occurring substance on Earth.
When diamond crystals are formed, gas bubbles become trapped inside them, where they form an intersecting pattern. This causes diamonds to gleam like stars. This gleam is known as asterism. (“Aster” comes from the Greek word for star.)
Diamonds conduct heat better than any other naturally occurring material on Earth. This property, as well as their hardness, means that have industrial value.
Graphite, the material used in pencils, is also made up of carbon atoms. However, graphite and diamonds are very different from each other because of their different crystals structures.
Rubies and sapphires are chemically identical. Both are made up of combinations of oxygen and aluminum. Their different colors are caused by traces of impurities. Chromium atoms cause rubies to be red. Iron and titanium are what make sapphires blue.
Emeralds consist of oxygen, silicon, aluminum and beryllium. Traces of titanium and chromium atoms make them turn green.
Precious Metals
Precious metals are rare, naturally occurring metals with great economic value.
The most well known precious metals are gold, platinum and silver.
Gold and platinum each make up about .0000005 of one percent of the Earth’s crust. Silver makes up only about .00001 of one percent
Gold has played an important role in international finance for a very long time. It has often been used as a form of money.
It is malleable, non-corrosive and a good conductor of electricity. This makes it extremely useful in industry.
Gold is usually found in the Earth’s crust as a relatively pure metal. It rarely forms chemical compounds.
A gold nugget usually contains about 8 percent silver and traces of other metals, including copper and platinum.
After platinum was discovered by Spanish explorers in the 16th century, it was used to make counterfeit gold ingots. Platinum was thought to be an adulterant that reduced the value of the ingots.
Today, however platinum is considered to be more valuable than gold.
Platinum has great industrial importance. It is resistant to corrosion and temperature distortion. This makes it very important to industry.
Although silver often forms compounds, such as silver chloride, its extraction from these compounds is usually unprofitable.
Therefore, like gold and platinum, it is used when it is found in its pure form.
Silver is the best electrical conductor on Earth. It conducts heat better than any other metal.