Augite

Augite is a common dark-colored clinopyroxene mineral found in mafic igneous rocks such as basalt and gabbro. Its composition varies, chiefly involving calcium, magnesium, iron, and aluminum.

Clinopyroxene: Clinopyroxene is a group of chain-silicate minerals that crystallize in the monoclinic crystal system. Augite is one of the most widespread members of this mineral group.
Basalt: Basalt is a fine-grained mafic volcanic rock rich in plagioclase and pyroxene. Augite is a frequent dark mineral in basalt’s groundmass and crystals.
Orthopyroxene: Orthopyroxene is a pyroxene group with orthorhombic crystal symmetry, commonly rich in magnesium and iron. Its orthorhombic structure contrasts with augite’s monoclinic structure.
Lunar basalt: Lunar basalt is volcanic rock collected from the Moon’s maria and composed chiefly of pyroxene and plagioclase. Some lunar basalts contain augite, linking the mineral to volcanism beyond Earth.
Silicate chain: A silicate chain is a structure formed by silica tetrahedra sharing oxygen atoms in a repeating line. Augite’s single chains organize its crystal structure.
Pyroxene: Pyroxenes are a group of rock-forming silicate minerals built from single chains of linked silica tetrahedra. The broader mineral family explains augite’s chain structure and common rock-forming role.
Gabbro: Gabbro is a coarse-grained mafic intrusive rock composed mainly of plagioclase and pyroxene. Visible augite crystals commonly occur with plagioclase in gabbro.
Pigeonite: Pigeonite is a low-calcium monoclinic pyroxene found in some rapidly cooled mafic rocks. Its lower calcium content distinguishes it from typical augite.
Mare Tranquillitatis: Mare Tranquillitatis is a basalt-flooded lunar plain in the Moon’s near side. Apollo 11 samples from this region include pyroxene-bearing basalts.
Solid solution: A solid solution is a crystalline phase in which different elements occupy the same structural sites in varying proportions. Element substitutions let augite vary in composition without changing its basic structure.

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