Microlite: Gemstone Information
Microlite is (Ca,Na)2Ta2O6(O,OH,F) and forms a series with pyrochlore.It occurs as euhedral to subhedral generally opaque to translucent pale yellow to brown, reddish or green octahedral crystals of the cubic system. The hardness is 5–5.5 and the SG normally about 5.5. The RI is 1.993–2.02; a degree of metamictization may lower the value to 1.93–1.94.Microlite occurs as a primary mineral in lithium-bearing granite pegmatites. Gem-quality crystals have been found at the Rutherford mine,Amelia, Virginia, USA; a transparent garnet-red specimen found in 1885 was faceted into a stone resembling red zircon (Arem, Color Encyclopedia of Gemstones, second edition, 1987).