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Extraordinary and unusual stones

Why don’t we talk about some of these?

Normally we’d cover the traditional gemstone colors – you know, white, red, blue and green (“the big four”) and call it quits. But humans need variety right now. We’re always hungry for something new, sick of eating the same old thing. So let’s change things up. Set out your tableware, put on the candles and prepare for a nouvelle experience in three courses. Bon appétit!

Hors d’oeuvre

We’ll begin with some fresh, cold Natural Blue Cobalt Spinel. It presents as normal, I know. You frequently see spinels such as gahnite and gahnospinel which look blue because of their zinc content. But that isn’t the case here. Natural Blue Cobalt Spinel is a rarity. And if, as a child, you wanted to stick your finger into that tempting jar of jam (the “forbidden” one) here is your chance to satisfy your desire to taste the exotic and unique. And our chef has really outdone himself. Natural Blue Cobalt Spinel is normally plucked from Tunduru in Tanzania or Vietnam (a most significant but ungenerous source). Today le cuisinier brought this delightfully chilled gazpacho (with difficulty!) all the way from Baffin Island, in the Canadian Arctic Archipelago.

Photo credit, University of British Columbia


Our central course comes from the warmer climate of Western Australia. Deliciously rare Variscite  with an unusually dark green shade due to the equally unusual presence of trivalent chromium, as the main chromophore agent. Our chef tells us the grains arrangement in the matrix is also unusual so this is a special dish, indeed. We know this hydrated, transparent translucent or opaque aluminium phosphate (normally light yellow-green-bluish) is common adornment in Germany’s Vogtland district, where it was found since Neolithic times. But, because of its rarity, it doesn’t usually appear in trade flows and is therefore unknown to most. Et voilà, yet another goodie for those seeking “forbidden” delights. And pleasant surprise, what a price (!) Only around 7 $ per carat when cut. Fortunately, our chef de cuisine was not concerned with the money, so much as the voluptuousness of the unusual to arouse our palates.

Un dessert mystérieux

From another warm location, at a different longitude, our final treat arrives from Mother Africa (although the discover will not tell us precisely where). Fewer than 10 years ago Greek researcher named Yanni Melas accidentally stumbled across something extraordinary: A material that looked much like low-quality opal, and was considered as such by the locals, coming in an intense natural (untreated) bluish green color that recalls turquoise, translucent, with a good 7.0 -7.5 on the Mohs hardness scale, refraction indices of 1.531-1.539 and density of δ=2.55-2.57 g/cm3.  Initially mistaken for chalcedony chrysoprase or for chalcedony chrysocolla, this mysterious material was finally identified as a new type of chalcedony, never found before, and dubbed “Aquaprase” – by Melas himself.

Photo credit, JCK Online

In Yanni’s intentions, the gem was named after a color combination of blue (water) and green (prasio, in Greek). Add a dash of excellent mechanical and photochemical stability which prevents fracturing or discoloration and its price of 1-100 $ per carat, depending on quality, presence or absence of matrix, etc., is more than justified. Best of all? Aquaprase is truly one of a kind. So far we had never seen any chalcedons that owe their color to the combined presence of chrome and nickel. As if that were not enough, while having the traditional crystal aggregate structure of normal chalcedony, our gem has some structural peculiarities of its own under the microscope, reported as “significantly different from chalcedony chrysoprase or other chalcedony varieties.”

At this point all we can do is lift up our praises to Melas, grateful for his valuable contribution to our beloved world of gemstones, while forgiving him for not providing any details on the location of the magical site (to just say “Africa” is obvious reticence), which we are maliciously inclined to limit to the Horn of Africa, more precisely Ethiopia. After all, where else can I find opal in Africa?

Photo credit, JCK Online


Luigi Costantini

Dr. Luigi Costantini is a pioneer in Italy’s gemological landscape and a leader in the European gem and jewelry industry. He established IGI's School of Gemology in Italy in 1998 and was instrumental in its development and expansion throughout the country. He remains honorary president of IGI Italy.

This Post Has 5 Comments

  1. Safy

    Zomerald and diamonds are a pure green zemerald color

  2. Abdalla Bakhit Ahmed

    Opal is my favorite colored stone.

  3. Javeriya Naje, GIA Diamonds Graduate, AJP

    I would like to write for IGI GEMBLOG. How can i submit an article?

  4. Fleur Pinto


  5. What’s up, I check your blogs on a regular basis. Your writing style is awesome, keep doing what you’re doing!

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