felspar

Everywhere were little grains of felspar, mica, or quartz, which caught the reflection of the light.

It turned evenly, slowly, noiselessly, and, as it turned, the light from the lamp caused the quartz and mica and felspar in the granite to glisten like a thousand fire-flies on a summer's evening.

The formation of new felspar in the hornfelses is pointed out as evidence of this.

This is a kind of hard porcelain made from a mixture of kaolin and felspar, in which the degree of hardness or fusibility is regulated by the proportion of one material towards the other.

Their felspar ranges from oligoclase to andesite and labradorite, and is often very zonal; sanidine occurs also in some dacites, and when abundant gives rise to rocks which form transitions to the rhyolites.