olivinephyric

Olivinephyric is a descriptive term used in petrology to classify igneous rocks. It specifically refers to rocks that contain phenocrysts of the mineral olivine. Phenocrysts are larger crystals that are embedded within a finer-grained groundmass. In an olivinephyric rock, these visible olivine crystals are a prominent feature. The groundmass itself can be composed of various minerals, depending on the overall composition of the igneous rock. Commonly, olivinephyric textures are found in basaltic or gabbroic rocks, but can also occur in other mafic and ultramafic compositions. The presence and size of the olivine phenocrysts can provide clues about the cooling history of the magma from which the rock formed. Rapid cooling often results in smaller phenocrysts, while slower cooling can lead to larger ones. The olivine crystals themselves are typically green in color and have a characteristic hardness and fracture. The term olivinephyric emphasizes the mineralogical and textural characteristics of the rock, differentiating it from other igneous rocks that may contain olivine but not as prominent phenocrysts, or rocks that lack olivine altogether.