Amphibole << AM fuh bohl >> is any one of a large group of relatively hard minerals found in many igneous and metamorphic rocks (see Rock). Many amphiboles are shaped like blades. Many are black, brown, or green, though they can be almost any color.
An amphibole called nephrite is the chief source of jade, which is widely used for fine carvings and jewelry. Amphibole asbestos is used in cement pipe and in filters that are resistant to harsh chemicals.
Amphibole crystals form in the monoclinic or the orthorhombic system (see Crystal (Classifying crystals)). They have pyramid-shaped units of silicon and oxygen that are linked in double chains.
