Axinite-(Fe) - Ca₂FeAl₂[BSi₄O₁₅](OH)

Habit: Usually gray to bluish gray, brown, honey brown or violet; less commonly green. Thin, wedge-shaped "ax­head" crystals common, frequently arranged in rosettes; also massive or granular. Vitreous luster; transparent to translucent. White streak.

Environment: Most commonly found in high-grade metamorphic zones, hydrothermal metasomatism of granite or aplite, and igneous contacts with sedimentary rocks.

Etymology: From the ax-head shape of the crystals and its iron content.