Class : Silicates
    Subclass : Nesosilicates
    Crystal system : Trigonal
    Chemistry : LiAlSiO₄
    Rarity : Rare

Eucryptite is a rare lithium and aluminum nesosilicate of lithiniferous pegmatites, in which it notably accompanies albite and other lithium minerals (spodumene, lepidolite, etc...). It is the silica-deficient equivalent of spodumene. Its name comes from the Greek eu (good) and kruptos (hide), because it is most often found embedded in albite. Eucryptite occurs in crystalline masses or aggregates, rarely in automorphic crystals measuring up to 3 cm, colorless, white, sometimes brownish. It is exceptionally exploited as lithium ore.

Main photo : Eucryptite from Foote, North Carolina, USA © Chris Emproto

Some eucryptite samples show polysynthetic twins with alternating thin and wide twin lamellae.

No fake listed for this mineral species.