Moonstone Africa: Gemstone Information 

Tanzania Found in pegmatites in the Kondoa District, Mkoyo, Zoissa, Mahenge and Morogoro. Fine material is translucent to sub-transparent with a brilliant blue sheen. Also as pale grey with lesser sheen and translucency. Some Tanzanian moonstones (alkali feldspar) show weak asterism: the stones exhibit cat’s eyes with a weaker ray perpendicular to the eye producing a four-ray star in some specimens. It has been called ‘sunstar’. High-quality albitic (RI 1.530–1.540; SG 2.62–2.64) moonstone exhibiting weak red fluorescence (SWUV) in pieces up to 300 ct and good transparency has been reported from the Morogoro region, Tanzania. Needle-like inclusions and twin planes can be seen particulary in cabochon material. It has, unconventionally, been used as a doublet top, altering the appearance of the pavilion colour and adding schiller. Previously the region only produced low-grade material. Madagascar A labradorite moonstone with blue sheen has been reported. RI α 1.550–1.553; γ 1.560–1.561; DR 0.008–0.010; SG 2.70.