kyanite

Kyanite is primarily used in technical, geological, and gemological contexts. It is characterized by its distinct bladed crystal structure and a rare physical property called anisotropy, where its hardness varies significantly depending on the direction in which it is scratched.

As a mineral name, it is typically treated as an uncountable mass noun when referring to the substance in general. However, it can be used as a countable noun when referring to specific crystal specimens or varieties of the mineral.