A calcium-poor pyroxene mineral occurring chiefly in basalt.
- Orthopyroxene forms in primitive (high-MgO) basalts but as differentiation proceeds, it is replaced by pigeonite once the enstatite component falls below 60 to 70 atomic percent.
- Various factors, including magma composition, control whether orthopyroxene or pigeonite occurs as the low-Ca pyroxene, but high temperatures yield orthopyroxene and low-pressure crystallization favours pigeonite.
- Pigeonite is the orthorhombic pyroxene equivalent in the volcanic rocks.
Early 20th century: named after Pigeon Point, Minnesota, + -ite1.
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