Amphibole

Amphiboles are inosilicate minerals built from double chains of silicate tetrahedra, commonly containing iron, magnesium, calcium, or sodium. Their varied compositions produce minerals found in igneous and metamorphic rocks.

Inosilicate: A silicate mineral whose tetrahedra form single or double chains. Amphibole is the double-chain branch of this structural mineral family.
Amphibole formula: A generalized chemical formula describing the variable site occupancy of amphibole minerals. Its sites show where major and trace elements enter the double-chain structure.
Petrography: The description and classification of rocks through their minerals, textures, and relationships. Amphibole textures and associations help distinguish igneous and metamorphic rocks.
Actinolite: A calcium-bearing amphibole ranging from iron-rich to magnesium-rich compositions, commonly green. Its composition and color make it a familiar member of the calcic amphiboles.
René Just Haüy: A French mineralogist who helped establish crystallography as a systematic science. His crystallographic approach shaped the study of mineral forms that includes amphiboles.
Silicate tetrahedron: A structural unit consisting of a silicon atom surrounded by four oxygen atoms. Linked tetrahedra form the chains that define amphibole structure.
Crystal structure: The ordered arrangement of atoms, ions, or molecules in a crystalline solid. Amphibole’s atomic arrangement accounts for its chain geometry and cleavage.
Amphibolite: A metamorphic rock composed chiefly of amphibole and plagioclase feldspar. This rock commonly records metamorphism of mafic igneous material.
Tremolite: A calcium-magnesium amphibole that contains little or no iron. It represents the magnesium-rich end of the tremolite–actinolite series.
James Dwight Dana: An American geologist and mineralogist known for influential mineral classification and textbooks. His mineral system helped standardize classification of amphibole species.

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