Gemstones that have a mineral origin are found in rocks, or in gem gravels derived from these rocks. Rocks themselves are made up of one or more minerals, and may be divided into three main types – igneous – sedimentary – metamorphic. The formation of rocks is a continuous process best described as the rock cycle (see left).
Igneous Rocks – have solidified from molten rock, which comes from deep beneath the Earth’s surface, these are “Intrusive” igneous rocks. Some called “Extrusive” igneous rocks, are thrown out from volcanos as lava, volcanic bombs and or ash. Essentially, the slower a rock cools and solidifies, the larger the crystals and therefore the gemstones.
Metamorphic Rocks – are either igneous or sedimentary rocks that have been changed by heat and pressure within the Earth to form new rocks with new minerals. As this happens, gemstones can grow within them. Sedimentary Rocks – are formed by the accumulation of rock fragments produced by weathering. In time, these fragments settle down and harden into rock once more. Sedimentary rocks are usually laid down in layers, and these may be shown as a feature in decorative stones.
Organic Gems – come from plants and animals. Gems such as Jet comes from fossilized wood. Coral comes from fossilized marine animals and Amber (see left) comes from fossilized tree resin , collected from soft sediments or the sea.
Whatever the gemstone you can be sure it has taken thousands of years to form. How can anyone not be impressed with something so beautiful that has taken so long to form? Gemstones are Mother Nature at her best!