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Spinel – the August birthstone

London Diamond and Emeralds

(The Black Prince ‘ruby’ adorning the Imperial State Crown)

For many centuries spinel has been mistaken for ruby, as its physical appearance and colour are obviously similar. The most famous example of this is the Black Prince Ruby, a spinel that enjoys pride of place in the centre of the Imperial State Crown of the British Crown Jewels. The name spinel is derived from the Latin ‘spina,’ which translates to ‘thorn’ and is thought to have originated from the pointed shape of most spinel examples. It is very difficult to distinguish spinel from ruby at first glance and their chemical and physical properties are also very similar so for many centuries jewellers and gem dealers would often work this to their advantage and sell the (slightly less valuable) spinel as if it were a ruby. With the advances made in gemmological testing since the work of Eduard Gübelin in the early twentieth century, it is now possible to easily identify the exact provenance of almost any gemstone. Furthermore in recent times spinel, once referred to as a ‘poor’ man’s ruby,’ has increased markedly in value and in many instances it is now deemed to be more valuable than ruby itself. Although most spinel are red, blue, green, orange, violet, yellow, purple, pink, brown, black and move specimens are also available. The red colouration is caused by the presence of chromium in the crystalline structure of the stone. After red, blue and pink are the most valuable stones. The various colours are created by the presence of different impurities in the chemical composition of the gemstone.

(It was only in the 1900s that ruby & spinel could be positively identified from one another)

Each colour of spinel has been christened with an identifying name. For example, orange stones are referred to as ‘flame’ spinel, blue are known as ‘cobalt’ specimens (these are highly desirable), red spinel is sometimes named ‘ruby’ spinel, ‘rubicelle’ are yellow, ‘balas’ pink, ‘almandine’ violet, ‘pleonast’ black and ‘picotite’ are brown. In terms of clarity, the more vitreous and transparent the lustre, the more valuable the stone. Eye clean and even some, very rare, loupe clean specimens can be found but as with many coloured stones, if it is too ‘perfect’ it may be synthetic so it is always worth obtaining a gemmological report from a renowned laboratory. Most spinel are brilliant cut and cushion cut examples are often the most aesthetically pleasing to the eye, and they also carry the advantage to the cutter of minimal carat wastage. Round, oval and emerald are the next preferred shapes. High quality red and blue examples of more than 5 carats are very rare and hence valuable, although some extremely rare specimens have been cut to over 25 carats. Spinel is actually rarer then ruby and its price is rising faster than almost any other coloured gemstone. Spinel is formed in octahedron crystals within igneous (volcanic) rock and metamorphic rock in contact with metamorphosed limestone. Spinel and ruby are found in the same rocks containing magnesium and aluminium, accounting for the confusion between the two.

(Pink spinel is the most well known)

Spinel are formed by the combination of both these elements and then ruby from the aluminium alone, once the magnesium has been exhausted. The finest spinel (and ruby) has been found in Myanmar (Burma), in particular from the much vaunted Mogok region, where production continues to this day. Sri Lanka is also a major producer of spinel, most notably of blue and violet varieties, and the island is also a major arterial route for spinel, ruby and other gemstones on their journey from countries across South East Asia to their end consumer markets in Europe, North America and the Middle and Far East. Thailand mines black spinel at Bo Ploi, Kanchanabur and it is also found in Madagascar. More recently production has got underway at mines in the Pamir Mountains of Tajikistan, Ontario Province in Canada and New Jersey and New York State in the USA. Over the years smaller scale, often artisanal mining of spinel has occurred in Afghanistan, Pakistan, Australia, Italy, Brazil, Sweden, Turkey, Russia, Vietnam and Tanzania. Due to the price increases over recent years, more and more synthetic examples have found their way onto the market, and there is much confusion over the fact that spinel is a naturally occurring coloured gemstone. Spinel has been an important part of Indian jewellery traditions for many centuries. The Mughal dynasties in particular were enthusiastic patrons of this most enigmatic of stones, choosing to adorn many of their crown jewels and fine collections with spinel.

(The remote Mogok valley in Myanmar is the origin for the finest spinel and ruby)

Spinel is most commonly set into 18 carat yellow gold, largely due to the fact that this is the best way to accentuate the depth of colour within the stone. Spinel also compliments diamonds well and is often used in conjunction with this stone because it interacts spectacularly with the scintillation (or ‘sparkle’) produced by the refraction on light through diamond. Spinel is also a very practical choice of stone for jewellery setting because it is a relatively hard 8 on the (1-10) Moh’s scale of hardness. This makes it a popular choice for setters and craftsmen, as they have less to fear from chipping, cracking or even cleaving (snapping) the stone as they work it into a jewellery creation. This hardness also means that spinel can be worn on a day to day basis by its owner with little danger of damaging it (providing sensible care is taken). Spinel is valued by jewellers and collectors alike for its vibrant colours, brilliant cut and impressive durability and workability on the bench. In some instances spinel can be found for less than a third of the price of comparable ruby of the same cut, colour, clarity and carat so it is an intelligent choice. Furthermore, its steady increase in value over recent years, coupled with limited supply, has created a situation in which it is likely that an example purchased today will rise sharply in price over the foreseeable future. Ironically this stone, mistaken for ruby for many centuries, is now starting to outshine its erstwhile cousin!

(Spinel is fast becoming a key theme in many of the fine jewellery houses’ collections)

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