A few years ago we acquired some unusual specimens from the estate of a collector who had travelled the world acquiring rare minerals. Among them were some large gemmy crystals in a vivid purplish red that we had never seen before. The material was labelled as originating from Spain.
We faceted several pieces and were delighted with the color saturation and translucency. The cut stones displayed a wonderful glow when backlit. But we noticed the material was fairly soft. So we suspected it might be a form of Calcite. We took a polished gem to GIA in Bangkok for testing and they confirmed it was Cobaltocalcite, a rare Calcite colored by trace amounts of cobalt.
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| Cobaltocalcite Rough and Polished |
GIA was so intrigued by this material that they requested samples of the rough material to do additional analysis in their lab. They wrote up their findings in the GIA journal, Gems & Gemology. They discovered that the unusually vivid color of our cobaltocalcite was due to high concentrations of cobalt with possible contribution from traces of manganese.
In addition to their usual reports, GIA has issued special Notable Letters that testify to the rarity of this material. Here is an excerpt:
"Gem quality cobaltocalcite may be recovered from many sources around the world, but the vast majority of material from all these sources usually produces an aggregrate of small closely packed crystals on a rock matrix or larger single crystals of lower quality. Rough crystals that will cut large fine stones are occasionally found but are in the minority. Very fine, large gem-quality cobaltocalcite ... with good transparency and distinctive saturated color can be considered extremely scarce. The large size, highly saturated reddish purple color and high degree of transparency makes this a notable cobaltocalcite."
We now are pleased to offer a small number of these world-class gems to collectors, including GIA reports and special Notable Letters.
See our collection of Rare Cobaltocalcite from Spain
Notable Gems from the AJS Collection
This month we feature rare collector gems, including Cobaltocalcite and Sphalerite from Spain, Pink Morganite and Sphene from Madagascar and Brazilianite from Brazil. Click on any gem photo for details.
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This gem is notable for its highly saturated color and superb translucency, with an amazing glow when backlit. Gem-quality cobaltocalcites over 10 carats are very rare, especially in this vivid color. This fine specimen will delight the most discerning collector. Guaranteed natural and untreated by GIA, including a Notable Letter which states that "Very fine, gem-quality cobaltocalcite with good transparency and distinctive saturated color can be considered rare. The color, transparency and large size make this a notable gemstone."
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A fine gem Cobaltocalicite with highly saturated color and superb translucency, with an amazing glow when backlit. Gem-quality cobaltocalcites in large sizes are very rare, especially in this vivid color. This fine specimen will delight the most discerning collector. Guaranteed natural and untreated by GIA, including a Notable Letter which states that "Very fine, gem-quality cobaltocalcite with good transparency and distinctive saturated color can be considered rare. The color, transparency and its size make this a notable gemstone."
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An outstanding large Sphalerite from the Aliva mine in northern Spain. This gorgeous round sphalerite is over 14 mm in diameter and is amazingly bright and fiery, with flashes of orange, yellow and green as it is turned in the light. Beautifully cut and very clean, this is a superb gem Sphalerite for your collection. Guaranteed natural and untreated. |
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A truly exceptional Pink Morganite from Madagascar, one of the finest we've ever seen. This outstanding gem displays a saturated pink that is rarely found in Morganite. This is perfectly clean material fashioned in a precison emerald cut. A wonderful gem for a special piece of jewelry. Guaranteed natural and untreated. |
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An ultra-rare Bi-Color Sphene from Madagascar! This unique bi-color displays outstanding color separation with vivid green and orange regions. This is very gemmy material with only slight inclusions; this gem will mount up virtually clean when set. A real treasure for the Sphene collector. Includes a certificate from the Asian Institute of Gemological Sciences (AIGS). |
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A rare gem Brazilianite in a very large size, nearly 13 carats. The color is a vivid yellowish-green with exceptional brilliance and excellent fire. This is fine transparent material, but there are some minor inclusions which are mainly visible only under magnification. This is an unusually large specimen that would be a notable addition to any rare gem collection. Guaranteed natural and untreated.
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News from AJS and the Gems World
Ask the Gem Experts
Each month we answer questions from our customers. We welcome your questions and you can submit a question from our contact page.
Are certain gems usually set in white gold and others in yellow gold? How do I choose the right colour of gold for my gemstone? LV, Canada
