Spinel is a wonderful stone that is available in a huge array of colours; both Spinel and synthetic Spinel measure 8 on the Mohs scale and have cubic crystal systems. 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; red Spinel was previously thought to be a variety of Ruby. Spinel and ruby are similar chemically; Spinel is magnesium aluminum oxide and ruby is aluminum 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 the red colour is desired.
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.
Because there are both natural and synthetic Spinels, people tend to think “synthetic” when they hear Spinel. Fine spinels are now rarer than the rubies they used to imitate, and yet they 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 Spinel in large sizes is the most expensive – but compared to a ruby of the same size and colour, a red spinel would be considerably less costly.
Spinel 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.
I think that one of our Cambridge designers may be working on a beautiful grey spinel engagement ring, so keep your eyes peeled…