Hiddenite

Hiddenite is the emerald-green, chromium-bearing gem variety of spodumene, a lithium aluminium pyroxene. It was first described in the 1880s from Alexander County, North Carolina, and named after the mineralogist William Earl Hidden. True hiddenite owes its green to chromium; paler yellow-green spodumene is more abundant but less valued.

Properties

Spodumene is monoclinic and forms flattened prismatic crystals with perfect prismatic cleavage, which — combined with a hardness of 6.5–7 — makes hiddenite a challenging stone to cut. It is transparent and strongly pleochroic, showing different green tints along different crystal directions. Its better-known sister variety is the pink-to-lilac kunzite.

Occurrence

Gem spodumene forms in lithium-rich granitic pegmatites. Besides the original North Carolina locality, fine spodumene comes from Afghanistan, Pakistan, Brazil and Madagascar, though chromium-coloured hiddenite specifically remains scarce.