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Gemology: I is for...

This week we're continuing our delve into gemology with gemstones beginning with I. Welcome to the world of Idocrase, Imperial Topaz, Inca Rose, Iolite, and Ivory.

Idocrase (Vesuvianite) Idocrase is another name for Vesuvianite, which was named for Mt Vesuvius in Italy, the place where it was first described after being found near lava flows. In fact, Vesuvianite is the more common name for this mineral with Idocrase now only being seen in old text books and indexes. Idocrase is generally a dull gem, often in shades of brown and yellow, but there are some instances of highly coloured and vibrantly radiant gemstones out there. These rarer lustrous colours, found in Quebec, occur in shades of red, pink, orange, purple and blue, and – even more rarely – several shades all at once!

Idocrase Vesuvianite Crystal

Imperial Topaz Imperial Topaz, also known as Precious Topaz, is a rare, highly collectible crystal gemstone with colours described as 'the setting sun' – a glorious pinkish-orange! It gets the name Imperial Topaz from the Russian Tsars in the 17th century who claimed all rights to any samples mined in Russia. Nowadays samples found in yellow, pink and purple are accepted as Imperial Topaz by analysis of their hardness on the Mohs scale and crystal structure. Imperial Topaz makes a fantastic gemstone for jewellery, being cut into many faceted gemstone shapes.

Imperial Topaz Uncut Crystal

Inca Rose (Rhodchrosite) Inca Rose is the more common – and romantic sounding – name for Rhodchrisite. Inca Rose occurs in crystals of light pink to deep red and is found in many countries, though interestingly mainly in the southern hemisphere.

Inca Rose, not to be confused with rose quartz, is often veined and works well polished en cabochon for jewellery and decoration. The largest single crystal found was discovered in the Sweet Home Mine, Colorado, in 1992. Known as the Alma King, this Inca Rose crystal measures 15cm in length. Inca Rose has also been found in stalagmites and stalactites in old Inca silver mines in Argentina, where it is often cut into slabs for sale.

Polished Cabochon Gemstone of Inca Rose

Iolite (Cordierite) Iolite is the name given to the gemstone quality variant of Cordierite. Cordierite generally occurs as a dull opaque mineral, but Iolite is a blue to deep blue gemstone that has enjoyed a great rise in popularity in recent times. Previously only known in a non-gemstone quality, that all changed when a large gem-quality deposit was found in Palmer Creek, Wyoming, in 1996. Wyoming is also credited with yielding the largest Iolite gemstone crystal ever discovered, weighing in at over 24,000 carats! Now that's some rock! Iolite is often mistaken for many other blue gemstones, including sapphire, tanzanite and blue spinel, but analysis of it's composition can help with proper identification. Iolite is also sometimes known as Lynx Sapphire or Lux Sapphire.. Did you know, legend has it that Vikings used thin slabs of Iolite as a navigation tool, enabling them to locate the sun on cloudy days.

Iolite Faceted Crystals

Ivory Ivory, being an organic material, like pearl, is not typically classified as a gemstone but it has been used in jewellery manufacture for millennia. In fact, samples of carved ivory have been found dating back 32,000 years! Ivory is the continually growing tooth material of tusked animals like elephants, walruses, and boars. Whilst originally a bye-product sourced from animals hunted for food, it's rise in popularity and value saw it become the most-prized part of the animal and led to an explosion in the hunting of these animals for their ivory alone. With elephants pushed to the brink of extinction, many countries introduced a law prohibiting the sale of 'new' ivory (antique pieces could still be sold) in a bid to curtail the poaching. At Alyssum Jewellery we do not advocate the use of ivory for jewellery, or for any other purpose other than as nature intended for the animal it was attached to! Artificial ivory is a great substitute and far more durable than improperly stored natural ivory, which can shrink and crack without proper care.

Carved Ivory Comb of St Heribert, 850-900CE

Next week: "How to Adjust Your Clip-On Earrings" If your clip on earrings are too loose or too tight, we can show you how to adjust them for the perfect fit.

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