This glossary contains simplified definitions for technical terms used within this site. For more complete, technical definitions, click here . A narrow crack in rock along which there has been no significant movement of either side.
Joints commonly form in parallel sets.
An aluminum-rich, blue to light green silicate mineral. Kyanite forms in metamorphic rocks at moderate temperature and high pressure. A type of mudflow that originates on the slopes of volcanoes when volcanic ash and debris becomes saturated with water and flows rapidly downslope. A metamorphic mineral that forms only under very high pressure. It is a calcium aluminum silicate and usually forms microscopic crystals.