Montebrasite (rare)

Item Description

A notably sharp, and well-formed, (un-etched), large, gemmy, soft yellow color, layered crystal group of the rare phosphate Montebrasite from the lesser known locality at Fazenda Pomarolli (fazenda is the Portuguese word for farm, so this would be the Pomarolli farm). The piece is not 100% crystallized all the way around as the back has some remaining pocket material, but it does have smooth sharp faces on the front. My favorite aspect of the piece is that it's actually crystallized! and not just an etched "lump" like the few I've seen from this locality. There are not many localities in the world that produce crystals of Montebrasite this size, and Brazil is still the single most productive country in terms of the amount of Montebrasite discovered. Please note that this is not Amblygonite, which was a typical labelling mistake that took place with this material years ago. It turns out that true Amblygonite is actually quite rare. The species are isostructural and are both lithium aluminum phosphates, but the difference is that Montesbrasite has a hydroxide ion in its chemical formula, while Amblygonite has a fluoride ion. In terms of charge and size, the fluoride ion resembles the hydroxide ion, so it's easy to see why so many Montebrasites were labeled as Amblygonites back in the day. As a matter of fact, Amblygonite was mistaken for Scapolite many years ago, which is actually how Amblygonite got its name. Exactly 200 years ago (in 1817), Amblygonite was named from the Greek word "amblus" for blunt, and "gonia" for angle, because of the obtuse angle between the cleavages, which distinguished it from Scapolite.