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an effusive rock composed of augite and olivine. Pi-crite also contains admixtures of hornblende, biotite, and or-thopyroxene and of various secondary minerals, including ilmenite, magnetite, and apatite. The olivine is often altered and replaced by serpentine, as well as by iddingsite, chlorite, and sometimes actinolite.
Picrites are holocrystalline. However, they sometimes contain a certain amount of glass inset with augite and olivine (picrite porphyry). The chemical composition of picrites is 38–41 percent SiO2, 5-10 percent Al2O3, and 20-29 percent MgO.