Transparency Crystals are opaque. The aggregates form radial sprays or randomly dispersed individual hairs. Also seen as fibrous coatings and rarely found in granular masses. Millerite is one of several minerals that is found in iron-nickel meteorites . Cleavage is perfect in several directions but is rarely discernible due to the extremely thin crystals.
Fracture is uneven.
5.3 - 5.5 Streak is dark green to almost black. Best Field Indicators crystal habit, associations and environment, color and luster.