WHAT ARE GEMSTONES

There are over 3,000 different minerals, and only around 50 of these are commonly used as gemstones. Some gems are not suitable to wear because they are too soft and scratch far too easily.

A few gems, like pearl or amber come from plants which are known as organics. These gem materials are produced by living organisms, and their sources are as diverse as shellfish (which produce pearls), polyps (whose skeletal remains form Coral), and the fossilized tree resin (which makes Amber). Ivory and Jet (this is a fossilized wood found in some sedimentary rocks) and shells are also organics, but are not stones, and are not as durable as mineral gems.

Others are called synthetics, these do not have a natural origin, but are man made in laboratories. These have very similar physical properties to natural gems, and may be cut to imitate the real thing.

A gem stone has three requirements, beauty, durability and rarity.

How are Gemstones formed

Gemstones that have a mineral origin are found in rocks, or in gem gravels derived from these rocks. These rocks are made up of one or more minerals, and maybe divided into three main types. The formation of these three types are igneous, sedimentary or metamorphic. This is a continuous process, best described as the rock cycle. Gem quality minerals within these rocks may be easily accessible at the earth’s surface, or lie buried deep beneath it. Others get separated from their host rock by erosion and are carried away by rivers to lakes or the sea.

Igneous rocks have been solidified from molten rock. Some rocks are thrown out from volcanoes as lava, volcanic bombs or ash, this is known as “extrusive”. “Intrusive” rocks are those that solidify beneath the earth’s surface, and the slower the rock cools and solidifies, the larger the crystal.

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. When this happens the gemstones can grown within them, for example, Garnets, Marble and sometimes rubies.

Sedimentary rocks are formed by the accumulation of rock fragments produced by weathering. These fragments eventually settle down and harden into rocks once more. Sedimentary rocks are usually laid down in layers which you can find in many decorative stones, for example, turquoise, Australian Opal, Halite and Gypsum.

Gemstones can be found all over the world, for example, Aquamarine is found in Brazil, Russia, Madagasca and Afghanistan, Peridot is found in USA, China, Burma and Egypt, Garnet is found in Brazil, Russia, East Africa, and India etc.

AGATE (Chalcedony)

Agate occurs in nodular masses in rocks such as lavas. When the rock is split open, it reveals amazing colours and patterns and has a distinct curved banding which distinguishes agate from other types of agate. Colouration is due to different quantities of trace elements and the banding is due to the progressive solidification of the material. Some agate may have black inclusions (manganese dioxide), green (chlorite), red (iron) or a mixture, for example, Moss agate or mocha stone. Fire agate has iridescent colours which are produced by the interference of light.

Onyx, Sard and Sardonyx (Chalcedony)
Onyx and Sardonyx is similar to agate, and a varieties of the microctystalline quartz, chalcedony. Onyx is similar to agate but is has straight rather than curved banding. Sard is a brownish red variety also similar to agate. Sardonyx is a blend of Sard and Onyx and has straight white bands of onyx and the brownish red of sard. I have to say that this is one of my favourite stones, it comes in many shades and is very beautiful.

I hope this gives you a small insight of where and how gemstones are found and formed.