Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters...

Gotthard.[better source needed] A solid solution of the plagioclase feldspar oligoclase +/− the potassium feldspar orthoclase also produces moonstone specimens...

Sunstone is a microcline or oligoclase feldspar, which when viewed from certain directions exhibits a spangled appearance. It has been found in Southern...

silica and related volcanics such as andesite. Oligoclase is common in granite and monzonite. The name oligoclase is derived from the Greek olígos ('small,...

Osumilite Otavite Ottrelite Otwayite Varieties that are not valid species: Oligoclase (a mixture of albite and anorthite) Onyx (a monochromatic banded variety...

follows (with percent anorthite in parentheses): albite (0 to 10) NaAlSi3O8 oligoclase (10 to 30) (Na,Ca)(Al,Si)AlSi2O8 andesine (30 to 50) NaAlSi 3O 8 – CaAl...

plagioclase is typically intermediate to sodic in composition, andesine to oligoclase. Quartz is present in significant amounts. Biotite and/or hornblende constitute...

variety of tonalite in which the plagioclase is mostly in the form of oligoclase. Trondhjemites that occur in the oceanic crust or in ophiolites are usually...

feldspar is pink microclineperthite and much lesser amounts are white oligoclase. There are lesser quantities of biotite, garnet, molybdenite and fluorite...

igneous rock – A form of tonalite where plagioclase-group feldspar is oligoclase Tuff – Rock consolidated from volcanic ash Websterite – Ultramafic and...