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A Stone to Screen You

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Фото © wikimedia.org/Kora27

For as long as four centuries, even the most experienced geologists were mistaking this mineral for a precious stone. There was a great potential for sphalerite: some samples were even more expensive than diamonds. Unfortunately, everyone had fallen for a thought the stone was a ”fake” and, consecutively, it was left forgotten for hundreds of years.

It is hardly surprising that mine diggers confused sphalerite with other minerals - at times it shines four times more intensely than diamonds and its outward appearance is almost identical to the one of a ruby. Back then, very few miners knew zinc could be smelted out of sphalerite. Most of treasure hunters thought it was nothing but a strange rock formation and threw valuable samples straight into the waste dumps. It took no less than three hundred years for a stone to receive an official name - partly because of its unfixed attributes; sphalerite varies not only in colour but also in the lustre and crystal shapes.

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Фото © Форпост Северо-Запад / Горный музей

Over the years, the stone has found its way into a variety of application fields. One of them is security maintenance and human life protection. Sphalerite glows under X-ray lights, and thanks to this property it is in use in X-ray machines where it is applied for luggage and cargo screening, thus helping officials to detect weapons, drugs and explosives.

Due to the high zinc content in this mineral, it has been historically used for the preparation of potions and drugs. Sphalerite powder was thought to help with digestion issues and sleep disorders. Folk medicine claims that healing properties of the stone depend on its colour - black-coloured samples cure the common cold whereas yellow ones steady nerves. Sphalerite zinc is still actively used in medicine as it is present in some anti-inflammatory agents. Zinc ointment is applied for treating eczema and dermatitis.

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Фото © Форпост Северо-Запад / Горный музей

Sphalerite is by no means an ideal gem stone though. The problem is in its hardness which results in difficulty of gem-cutting. Scratches appear on the mineral’s facets and its lustre gets lost. Nonetheless, even though this stone is almost never used in jewellery due to processing complexity, some of the samples are highly valued by collectors. Some of the samples achieving over 20 carats in weight can be priced as high as 10.000 USD. Sphalerite of high quality is mined at the world’s only deposit, in the US. It is the only place where samples suitable for use in jewellery production can be found. These specimens of sphalerite stone are named cleiophane.

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Фото © wikimedia.org/Didier Descouens