Friday 22 January 2021




ere’s for eccentricity.
Outside of mineralogical and metaphysical circles it’s a pretty safe bet most people have never heard of any of these.
Alphabetically they are evenkite, hackmanite, haüyne, icosahedrite, lonsdaleite, muromontite, pezzottaite, proustite, shungite, and thortveitite.
The single cut specimen of that last item, named Deep Thought by its discoverer, is especially perplexing in that we can be absolutely sure it’s either (1) a genuine, once-in-a-lifetime anomaly, or (2) a clever though unfathomable hoax.
Skip to: Evenkite ✧ Hackmanite ✧ Haüyne ✧ Icosahedrite ✧ Lonsdaleite ✧ Muromontite ✧ Pezzottaite ✧ Proustite ✧ Shungite ✧ Deep Thought
There are three more ultralight hydrocarbon minerals akin to evenkite and similarly obscure. In order of increasing weight they are dinite, fichtelite, and hartite with densities approximating 1.02, 1.03, and 1.05 gm/cc respectively. Fichtelite has 19 carbons; both dinite and hartite, 20. All three are colorless when pure and show up in petrified wood. Dinite comes from Tuscany, fichtelite from Bavaria, hartite from Tuscany and Austria.
A member of the sodalite or “Princess Blue” group, hackmanite distinguishes itself by the additional presence of sulfur in its makeup. Though discovered in Greenland way back in 1896 it’s still relatively unknown. It’s too soft for a ring or any other application that may take much of a beating, but fine for something like a pendant. It glows orange to red under UV.
That splendor comes at a premium, though, since like hackmanite haüyne’s fragility (a Mohs hardness of 6.5 to 7 combined with some brittleness) largely confines it to pendants, brooches and such, or genteel show-and-tell among collectors of the exotic. René Just Haüy (1743-1822) was a pioneer in crystallography and narrowly missed the guillotine during the French Revolution.
A good visual analogy would be the Penrose floor pattern you see to the left. Each tile connects to its neighbors according to strict rules, yet no matter how hard you look you’ll find no periodic replication in any direction.
Icosahedrite was found in Russia’s Kamchatka region in the form of tenth-millimeter grains mixed with serpentine. It’s an opaque, metallic-looking compound of aluminum, copper, and iron. Along with everything else, researchers are now certain icosahedrite is extraterrestrial. The bodies that brought it here were carbonaceous chondrites roughly similar in composition to Mars’s moons Deimos and Phobos.
Lonsdaleite’s name honors diminutive X-ray crystallographer and chemistry professor Kathleen Yardley Lonsdale (1903-1971). “It makes me feel both proud and rather humble that it shall be called lonsdaleite,” she remarked. “Certainly the name seems appropriate since the mineral only occurs in very small quantities (perhaps rare would be too flattering) and it is generally rather mixed up!”
Among radio-minerals, muromontite is a special case. A particular Swedish variety of it juxtaposes its uranium (element 92) with beryllium. As the uranium decays, some of the alpha particles it radiates get absorbed by the beryllium. The beryllium in turn ejects protons. When a not-yet-decayed uranium nucleus gets a square hit from one or more of those, it can transmute up to plutonium (94), or even more rarely neptunium(93) and americium (95). Naturally occurring transuranics like these lie far below any rational threshold of concern. What’s troubling is the 20 tons or so of plutonium the nuclear industry churns out annually.
Dr. Federico Pezzotta is Curator of Mineralogy at the Museum of Natural History in Milan. He lectures widely and has authored or co-authored Beryl and Its Color Varieties, Madagascar: A Mineral & Gemstone Paradise, and The Italian Island of Elba: A Mineralogical Jewel in the Tuscan Archipelago.
The reason for this cloak and dagger is that proustite is nature’s version of photographic film. Freshly excavated, the choicest crystals are transparent and spectacularly red with a metallic luster. But intemperate exposure to light over time makes them cloud up and blacken permanently. Proustite is a compound of silver, arsenic, and sulfur and you’re basically seeing the silver take over.
In or out of the dark this mineral is much too delicate for any kind of jewelry and although a wary cutter may facet it occasionally — for the sake of novelty — most collectors would freak out at the notion of sacrificing their specimens that way. Proustite gets its name not from Marcel but Joseph Proust (1754-1826), a French chemist who established the Law of Proportions for compounds.
So what’s your favorite form of coal?
But one thing that makes shungite quite special for a mineral is that it most certifiably contains fullerene molecules. Those are the hollow spheres of carbon atoms, first identified in 1980 and subsequently named after futurist and geodesic dome inventor Buckminster Fuller.
ne fine day in 2004 a purplish pebble turned up in Bangkok in a batch of rough gemstones from Africa.
It fell to the floor at one point and split off a fragment, which was saved.
After the stones were all cut, a routine series of tests revealed that the purplish one didn’t resemble anything previously known.
But no one has ever seen that mineral in the form of a beautifully clear, facetable gemstone. Unless other thortveitites have been floating around, misidentified as other species, this would be one-in-a-trillion. Ultrapure thortveitite can be synthesized, to be sure, but this stone shows mild inclusions suggestive of a natural source.
It shouldn’t be hard to fake a river-jostled pebble with a few imperfections. But then how could such an object have ended up in that package of rough, with the perpetrator assured ahead of time it would be noticed and so painstakingly analyzed and announced to the world? And how would he or she have ever profited? It’s been quite a few years now and no other specimens like Deep Thought have surfaced.
9 September 2018
Hi Peter,
Thank you for drawing attention to the discovery of this beautiful and rare gemstone.
It’s disappointing that more has not been reported as it makes it very creditable gem.
I believe wholeheartedly that it is of natural origin as I cut the stone that is pictured in the article. I noted a substantial number of attributes such as anomalies in the crystal lattice which were not easily photographed. This further supports the stone is natural.
Ross Chapman
FGA
Hackmanite photo ☆ Mauro Pantò of thebeautyintherocks.com;
Lonsdaleite imagery ☆ Eric Baird;
Muromontite photo ☆ Theodore W. Gray;
Haüyne and Pezzottaite photos ☆ Dr. Robert Lavinsky of iRocks.com
Thortveitite photos ☆ Ross Chapman.