A calcium-poor pyroxene mineral occurring chiefly in basalt.
易变辉石
Example sentencesExamples
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.
This contrasts with the first-order character for the HT phase transition in pigeonite containing significantly less calcium.
There appear to be a number of different possible mechanisms for the pigeonite - orthopyroxene transformation.
Pigeonite is the orthorhombic pyroxene equivalent in the volcanic rocks.
Origin
Early 20th century: named after Pigeon Point, Minnesota, + -ite1.