Brazilianite: Gemstone Information
Brazilianite, fine transparent yellow at its best and still a comparative rarity was first reported in 1944. It occurs in phosphate-rich zones of granite pegmatites, the only gem-quality material coming from locations in Brazil. The original find was in the Conselheira Pena area of Minas Gerais. Brazilianite is a hydrous sodium aluminium phosphate NaAl3 (PO4)2 (OH)4. It crystallizes in the monoclinic system forming characteristically equant or spear-head shaped crystals. There is a good cleavage and the hardness is 5.5. The SG is usually 2.98 and the RI for the alpha, beta and gamma rays is 1.602, 1.609 and 1.621–1.623,biaxial positive with a birefringence of 0.019–0.021. The dispersion is low at 0.014.Brazilianite is brittle and shows a conchoidal fracture. There is no recorded response to UV and there is no useful absorption spectrum in the visible. The dichroism is insignificant. Crystals are reported from Corrego Frio, north of São Tomé, Minas Gerais. In 1947, another source of brazilianite was discovered at the Palermo mine, North Groton, Grafton County, New Hampshire, USA.