How Are Gemstones Formed?
Many of us own beautiful pieces of handmade jewelry containing different gemstones. We refer to diamonds, emeralds, rubies and sapphires as precious gemstones because of their rare appearance and high value. All other stones are called â€œsemi-preciousâ€ even though the pieces containing the stone are certainly not! Ancient people even used gemstones as a form of currency. You may be able to appreciate the beauty of a gemstone, but have you ever wondered how it was formed?
Nearly all gemstones are formed beneath the Earthâ€™s surface. The process involved in the creation of the different stones can vary greatly. Many stones are formed when minerals react with the water that is near the Earthâ€™s surface and then dissolve. When this solution evaporates or cools, minerals form. Water that mixes with silica-rich rocks such as sandstone will produce gemstones such as amethysts, agates and opals. When copper-rich rocks mix with water, copper-bearing minerals such as malachite, turquoise and azurite are formed. Turquoise has been mined for more than 4000 years and ancient Egyptians considered the gemstone a very precious commodity.
Other gemstones such as emeralds and tourmalines are formed when rain water or water from cooling bodies of magma mix with minerals and then crystallize in open cracks or cavities. These spaces become filled with veins of minerals to create what is called hydrothermal deposits.
Magma is a mixture of crystals, dissolved gas and liquid rock beneath the Earthâ€™s surface. Zircons, topazes and rubies are created by crystallizing in the magma or gas bubbles that occur in volcanic rocks. This process produces what are known as magmatic gems.
Other gemstones are formed directly in the mantle. This layer makes up almost 70% of the Earthâ€™s mass and is made up of iron, magnesium, silicon, oxygen, aluminum and silicate compounds. The upper layer of the mantel contains a large volume of the olive-green mineral olivine. This is one of the most common of all Earthâ€™s minerals and transparent olivine is known as the gemstone peridot which is the French word for â€œolivineâ€.
The word â€œmetamorphicâ€ is defined as a metamorphosis or change of form. Metamorphic gems such as jade, garnet, aquamarine, emerald, ruby, sapphire, lapis lazuli, onyx and zircon are formed over time when rocks are altered by intense heat and pressure as well as interaction with solutions. Countries such as
Diamonds are sometimes formed in metamorphic rocks although this process is rare. Most diamonds come from volcanic rocks called kimberlite. These rocks are named after the South African town of
As you can see, the gemstones we have come to know and love in are formed in many different manners. Handmade jewelry containing these stones is usually more expensive because gems require a unique combination of chemical elements, pressure and temperature to form. Itâ€™s amazing to think that the processes occurring deep beneath the Earthâ€™s crust are able to produce such beautiful, colorful stones!