Color is colorless, white or stained yellow to brown by limonite. Luster is vitreous. Crystals are transparent to translucent. Crystal Habits include prismatic crystals with steep pyramidal terminations. Also pseudo-orthorhombic twinned prismatic crystals are common but tabular crystals are rare.
Cleavage is very indistinct.
Fracture is conchoidal. Streak is white. Associated Minerals include thomsenolite , cryolite , ralstonite and limonite . Notable Occurrences are limited to Ivigtut, Greenland. Best Field Indicators are crystal habit, associations, locality and lack of good cleavage.