Synonym: Amphibole group.
Clades:
Inosilicates;
Silicates;
Lapidae.
Crystal systems: monoclinic and orthorhombic.
MineralogyAmphiboles contain essential hydroxyl (OH) or halogen (F, Cl) and the basic structure is a double chain of tetrahedra (as opposed to the single chain structure of pyroxene). Most apparent, in hand specimens, is that amphiboles form oblique cleavage planes, around 120 degrees.
Amphiboles are also specifically less dense than the corresponding pyroxenes.
Amphiboles are the primary constituent of amphibolites.