Habit: Sky blue to azure blue. Velvet-, wool- or cotton-like aggregates and coatings composed of minute acicular crystals; also radial-fibrous or tufted. Silky luster; transparent to translucent. Pale blue streak.
Environment: A secondary copper mineral found sparsely in the oxidation zones of copper-bearing ore bodies.
Etymology: From the Greek words for "blue" and for "hair," in allusion to its color and habit.