Spinel
Spinel occurs in granite and metamorphic rocks, and is often found in association with corundum. The most popular colour is red, which is coloured by chromium and iron.
Synthetic Spinel has been manufactured since 1910. Both Spinel and synthetic Spinel measure 8 on the Mohs scale and have cubic crystal systems. They are also both available in an array of colours. The variety of colours are due to the presence of various impurities; such as iron, chromium, vanadium, and cobalt. The most popular colour is red, which is coloured by chromium and iron and previously thought to be a variety of Ruby. Other available colours are: orange, yellow, brown, blue, violet, purple, green, black. Clear spinel is VERY rare.
Spinel occurs in granite and metamorphic rocks, and is often found in association with corundum. They are found in places such as Burma, Sri Lanka and Madagascar; as well as sometimes in Afghanistan, Pakistan, Brazil, Australia, Sweden, Italy, Turkey, Russia, and the USA.
They can be improved in colour and transparency through heat treatment; and it is only one in a handful of natural gemstones that have not been treated.
Spinel and ruby are similar chemically; Spinel is magnesium aluminium oxide and ruby is aluminium oxide. This is probably why the two are relatively similar. Rubies are harder to find in a popular “pillar box” red colour, as they tend to be more pinky, so Spinel is often suggested as an alternative stone if that specific red is desired. In fact, fine spinel is now rarer than the rubies they used to imitate, and yet are more affordable.
Apart from red diamonds and rubies, Spinel is the most expensive red gemstone; although the prices do vary depending on size, quality, and colour. Red in large sizes is the most expensive – but compared to a ruby of the same size and colour, it would be considerably less costly.
This gemstone is most often faceted in oval, round, or cushions shapes, and is therefore used often in jewellery. It is sometimes cut in cabochons, which can rarely show a cat’s eye effect or asterism.
The origin of the gemstone’s name is uncertain, but it is thought to have come from the Greek for “spark” or the Latin for “thorn”. It is supposedly good for financial gains and protects the wearer against unforeseen losses.