- a glassy, often transparent variety of orthoclase in which sodium may replace as much as 50 percent of the potassium: forms phenocrysts in some igneous rocks.
Origin of sanidine
Examples from the Web for sanidine
Historical Examples of sanidine
All the upper part of the mountain is composed of a pumiceous tufa, rich in sanidine and of a characteristic greenish colour.A Study of Recent Earthquakes
They are rich in leucite, but contain also some sanidine and often much nepheline with hauyne or nosean.
They are of trachytic appearance, containing phenocysts of sanidine, leucite, augite and biotite.
Sanidine, san′i-din, n. a clear glassy variety of orthoclase.
It is remarkable for the large crystals of sanidine (glassy felspar) which it contains, and has a rude columnar structure.Volcanoes: Past and Present
- an alkali feldspar that is a high-temperature glassy form of orthoclase in flat, tabular crystals, found in lavas and dykes. Formula: KAlSi 3 O 8