Enstatite, hypersthene, and ferrosilite are members of the orthopyroxene solid solution series. All have low birefringence (first order red maximum), parallel extinction, and pyroxene 87 degree cleavage. Pale green, pale red, or pale purple pleochroism occurs in some grains. Distinguished from clinopyroxene by low order interference colors and parallel extinction. The photo above shows one cleavage and thin exsolution lamellae.
Orthopyroxene occurs with clinopyroxene in many igneous rocks, such as gabbro, diorite, basalt, andesite, and the peridotite family. It is an indicator mineral for the granulite and pyroxene hornfels facies of metamorphism.
Fine exsolution lamellae in orthopyroxene. Field of view 1.5 mm, crossed polarizers.
Petrography Home Minerals List Rocks List
