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The Stone and the Black Cats’ Eyes

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Фото © Форпост Северо-Запад / Горный музей

Until the early 19th century, this stone was often mistaken for emerald. But when the truth had been revealed, people's interest in the mineral only started to increase, for the rock turned out to be no less rare and highly-demanded.

Humanity got to know of dioptase already far in the past; researchers of Ancient Rome described it in their works, which date back to the first century AD. Russian people found out about the mineral from the merchant from Bukhara, Ashir Zaripov. The legend says he discovered dioptase deposits in Kazakhstan at the end of the 18th century.

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Фото © Форпост Северо-Запад / Горный музей

Transparent, dark teal, vitreous crystals were glowing as bright as emeralds, and they caused a perfect furore. An Englishman, who served in that area at the behest of Grigory Potemkin, Generalfeldmarschall of the Imperial Russian Army, was entrusted to deliver the stones to St. Petersburg. The samples were dispatched and then thoroughly analysed. Specialists from the Academy of Sciences, who were performing the analysis of specimens, identified the rock as a variety of emerald and named it ashirite.

Not everyone believed though that the mineral was related to emerald. An expedition headed by Russian traveller Herman left to explore the discovery area. Herman highly doubted that crystal facets of any type of emerald could wear out so easily. Besides, the mineral was very fragile. New samples gathered during the trip were submitted for further study to Toviy Lovitz, a Russian chemist from St. Petersburg. He discovered that dioptase by its composition significantly differs from emerald, particularly in terms of hardness. In fact, a similar colour is basically the only thing the two minerals share in common. Two years later, René Just Haüy, the French mineralogist, gave the mineral an official name - dioptase.

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Фото © Форпост Северо-Запад / Горный музей

But dioptase is not the only name under which the mineral was known. There actually have been over thirty of them! For example, it was called pseudo-emerald because of the stone's optical properties and its emerald green colour, hardly distinguishable from that of the eponymous mineral. The rock's other name is copper emerald, or also emerald malachite. This one comes from the fact that dioptase was all too often found in conjunction with azurite or malachite. Pavel Bazhov, a Russian writer, used the 'copper emerald' name throughout his book of fairy tales - in particular in his story "The Mistress of the Copper Mountain and other Tales". There the green-coloured stones turn into the eyes of the Mistress's black cats, which frighten the tale's antagonist, who behaves meanly towards his companions.

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Фото © Форпост Северо-Запад / Горный музей

The word 'dioptase' originates from the Greek, with dia meaning 'through' and optos 'visible' - combined together, 'visible through'. There is a meaning: cracks inside the rock samples are clearly visible. Scientists even tried to make use of the high transparency the stone possesses and put it to the manufacturing of lenses.

In our days the mineral is used as a pigment in icon painting: although not as a colouring agent, yet surprisingly enough as a means to outline the light-to-dark transition zone. The paint layer made of stone is transparent and is applied as a topcoat to create the effect of light and shade.

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Фото © Форпост Северо-Запад / Горный музей

There is no much use for dioptase in jewellery since the stone is very fragile. It crumbles easily, and therefore it is almost impossible to cut it. Hence dioptase is more prominent as an item of exclusive jewellery collections, usually in the form of rough crystals.

The mineral is mostly of value to collectors, primarily deriving from the fact that there are very few dioptase deposits worldwide. For that reason, any decorative object with dioptase is a highly sought-after product, with prices varying from several tens to thousands US dollars.

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Фото © Форпост Северо-Запад / Горный музей

Thus far, some fake emeralds have still been made using dioptases. The substitution for simulants is hardly a new phenomenon; such manipulations can be traced back to the times of Middle Eastern merchantry. Unfortunately, only a specialist can tell an imitation from a real jewel since determining whether the item is genuine requires prior studying of the sample's chemical composition.