From the Greek "kyanos," meaning "blue." It holds a rare mineralogical trait—hardness that changes with crystal direction. Mohs 4.5 along one axis, 7 along another. Within a single stone, hardness nearly doubles.

Formed under high-pressure conditions in metamorphic rock. Geologists use it as an index mineral: the presence of kyanite confirms that extreme pressure once existed at that location. The stone itself is testimony to the Earth's internal forces.

Sourced from Brazil, Nepal, and Kenya. Its crystals grow in flat, blade-like formations, so rough specimens often resemble thin swords.