Pegmatite vein containing gem minerals near Tonga Mountain, 15 km south of the town Betafo. An intensely kaolinized pegmatite cuts granitic-gneisses near their contact with amphibolized gabbroids. Large transparent crystals of blue
beryl are found, some of which have yellow or green tints or dark green cores. Spectacular druses of
smoky quartz and
aquamarine with brilliant faces are found within accumulations of red (pocket) clay. Black
tourmaline (
schorl)is common.
Garnets (almandine-spessartine series),
columbite,
betafite, metamict
zircon,
magnetite,
molybdenite (as inclusions in
quartz), and other minerals are present.
Ref: E.Ya. Kievlenko, Geology of gems, 2003, p. 112
Gemstone List