Spinel Garnet, Peridot, Sinhalite
Spinels sometimes do show asterism (4 rayed) when suitable stones are cut en-cabochon.
The most famous spinel is the Black Prince`s ruby adorning the crown jewels of the UK, long thought to be a ruby which on examination was found to be a red spinel in fact.
Fine red spinels are found in Russia and Burma while slightly lighter shades are found in Sri Lanka. Beautiful blue spinels have been found primarily in Burma and Sri Lanka as well as Madagascar. Spinels are also found in Brazil, Thailand and Australia.
Peridot : This is magnesium, iron silicate and one of the few stones in which the colour is caused by the colour causing element being a part of the chemical composition itself as against it being a trace element or “impurity’ as in most other stones. An attractive light green colour , this gem occurs in very few other colours. By the nature of its geren colour this stone is quite popular with the consumers.
Peridot is found in the island of Zerbeget, (where it was discouvered) in the Red Sea about 50 km. from Egypt and also in Pakistan, Afghanistan, Burma, USA, Australia, Brazil.
Garnet: These stones come in attractive blood red, cinnamon orange, emerald green, and even in colours resembling the extremely costly alexandrites when they are referred to as colour changing garnets.
In the late nineteenth century and right upto the mid twentieth most of the garnets the Europeans were familiar with were the Boehimian (from Czechoslovakia) garnets, an extremely dark red gem devoid of any luster.Even today the mention of the word garnet has a negative reaction from Europeans . However the garnets from several localities such as Burma, Sri Lanka, Madagascar have very attractive red hues with high luster and make fine Jewellery .Most of the red garnets are Pyrope, Almandine /Pyrope or the Alamndines. However it must be borne in mind that most of the garnets are a mix of one or more of these types and a really pure Pyrope or almandine hardly ever exists.
The green garnets are of two types, the Andradites to which the Demantoids belong coming mainly from Russia and (of late ) from Iran which surpass even Diamonds in their brilliance and the grossular from Pakistan and Tanzania which resemble emeralds .
The fine red-orange Garnets are either grossular or spessartite garnets, fine specimens of the latter resembling a good orange sapphire and commanding extremely high prices.
Garnets are found in India, Burma, Thailand, Sri Lanka, Madagascar, Brazil, Zambia,
Sinhalite: Named after the Sanskrit name for Sri Lanka this gem was long thought to be a brownish peridot but routine gemological testing showed that it had physical constants that deviated from that of peridot whence x-ray crystallographic and chemical testing was done to get to the bottom of the mystery. This showed a chemical formula completely different to that of peridot .
Sinhalite is very rarely found in localities other than Sri Lanka although off and on a few specimens have been found in Burma./div>