Typically sourced from Brazil (Minas Gerais),
Namibia, Mozambique, and Afghanistan, this is the blue variety of
tourmaline belonging to the elbaite series, colored by traces of Fe2+
and Ti in the lattice. It crystallizes in slow-cooling granitic pegmatites
during the Phanerozoic, often in association with quartz, lepidolite,
and other borosilicates. Trigonal system, elongated striated prismatic
habit, hardness 7–7.5 Mohs, density 3.0–3.2 g/cm³, strong pleochroism
(blue-green/dark blue dichroism).
A gemstone highly valued in jewelry for its intense blue
tones, sometimes mistaken for sapphire; sought by collectors for the
rarity of its more saturated hues; not to be confused with the (copper-
bearing) “Paraíba” variety , which is rarer and more valuable.