Montebrasite

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Montebrasite is a rare lithium aluminium phosphate hydroxide which forms a series with Amblygonite. Both occur in lithium-bearing granitic pegmatites. Remarkably, for a rare species, Montebrasite crystals to a metre in size have been recorded, but actually any sort of crystal is rare, and those larger crystals tend to be heavily distorted. Some of the best crystals have come from lithium-rich pegmatites in Brazil, and João Firmino claim, at Linópolis, Divino das Laranjeiras, Minas Gerais, where this specimen comes from, has produced some very good examples. This matrixless individual crystal is a quite substantial 6.8 x 6.8 cm in size and is from the the superb systematic collection assembled by the brothers Martin and Michael Günther (1951-2007 & 1956-2021). It is glassy, translucent to transparent and with a very pale yellow hue. The front crystal faces are well-formed, but around the edges the crystal is slightly serrated. Nevertheless, this is a good example of a rarely seen pegmatitic species.