Indicolite

Indicolite (also spelled indigolite) is the blue gem variety of elbaite tourmaline. Its colour ranges from pale sky blue through rich indigo to deep greenish blue, produced by iron and, in some material, traces of copper. Pure, saturated blue tourmaline is uncommon, which makes good indicolite a prized collector and gem stone.

Properties

It shares the tourmaline group's trigonal symmetry, prismatic striated habit, hardness of 7–7.5 and absence of cleavage. Indicolite is markedly pleochroic, often appearing darker or more green down the length of the crystal than across it, so cutters orient stones carefully to show the best face-up colour.

Occurrence

Indicolite occurs in lithium-rich granitic pegmatites with lepidolite, albite and quartz. Brazil, Madagascar, Namibia, Nigeria and Afghanistan are notable sources. Copper-bearing blue-to-green tourmaline of the Paraíba type is treated as a separate, exceptionally valued material. See also the red and green elbaite varieties rubellite and verdelite.