A mineral that grows in long, slender, needle-like crystals. The tendency of some minerals to split along smooth surfaces in definite directions.
Crystals are solid bodies bounded by smooth surfaces called faces, that meet in definite angles.
A form of luminous energy emitted when certain minerals are irradiated with ultraviolet light. The way in which a rock or mineral breaks. Minerals with a specific gravity greater than 2.87. An emission of light due to a stimulus like directed pressure, heating, rubbing, irradiation with X-rays, ultraviolet light, etc. The manner in which light is reflected from a rock or mineral's surface.