Ludwigite - Mg₂Fe³⁺O₂(BO₃)

Habit: Dark green to brown and black. Prismatic crystals; radiating plates or massive, fibrous or granular. Submetallic luster; opaque. Greenish black streak.

Environment: A high-temperature mineral occurring in contact metamorphic deposits.

Etymology: Named in honor of Ernst Ludwig (1842-1915), an Austrian professor of chemistry at the University of Vienna, who analyzed the original material.