Phantoms occur in many of the smaller transparent blue crystals, with a darker blue core and a colorless to pale blue outer zone. Color varies from pale to deep blue, pink to colorless to white. Luster is dull to vitreous to silky. Diaphaneity is transparent to translucent. Crystal Habits include short to long tetragonal prisms, crystalline masses.
Fracture is conchoidal.
Streak is white.