Axinite is not common, but it is worth watching for near granite bodies in metamorphic rocks. Collectors like it because it is a triclinic mineral that often has good crystals displaying the peculiar symmetry, or lack of symmetry, typical of this crystal class. Its "lilac brown" color is distinctive, showing here to good effect against the olive-green of epidote and the milky white of calcite. The crystals are strongly striated, though that isn't evident in this photo (which is about 3 centimeters across).
Axinite has an odd atomic structure consisting of two silica dumbbells (Si2O7) bound by a boron oxide group; it was formerly thought to be a ring silicate (like benitoite).
Axinite forms where granitic fluids alter surrounding metamorphic rocks, and also in veins within granite intrusions. The Cornish miners called it glass schorl—schorl being a name for hornblende and other dark minerals.