What is a gemstone?

Rough amber with sherry coloured topaz and yellow sapphire

Most gemstones are minerals – that is to say they are naturally occurring, with an identifiable chemical composition and regular internal structure.  Minerals are inorganic, created by heat and pressure in ancient volcanoes resulting in the fabulous colours and shapes of natural crystals forming deep in the earth.  There are over 3000 minerals but less than 100 are hard enough to be cut, polished and worn in jewellery.  Some are very rare, perhaps found in just one area of Africa, such as Tanzanite.  Others are often found with many other . – for example, garnet is often found in diamond mines – and yet there are also rare and precious forms of that same garnet family. Demantoid Garnet is an  extremely rare and valuable, vivid fiery green gemstone only found in the Urals.

Some gemstones are organic, such as pearls, coral, bone, ivory, jet and amber.  Some are the fossilised remains of bone, ivory or horn from pre-historic animals; or the sap, resin or wood  from ancient trees. Small, round calcium carbonnate beads are produced by certain types of fresh or saltwater mussel.  The mussel covers an irritation caused by a piece of sand or grit with calcium carbonnate and the process creates what we call a pearl.  Today, most pearls are cultured –  that is, they are farmed and a small bead is inserted into the mussel, which is then returned to the sea for many years until the pearl has been formed.

Coral is the calcified skeletons of tiny coral polyps that live beneath the sea on reefs and atolls.  The most popular coral is red but black white and even blue coral can be found, some growing to over 10 feet in height.

Rough amber with sherry coloured topaz and yellow sapphire:  photography by Paul Hartley, Hartley Studios:  www.hartlystudios.com