microfelsitic

Century Dictionary and Cyclopedia

1. The designation suggested by Zirkel for a devitrified glass when the devitrification has been carried so far that the hyaline character is lost, but not far enough to give rise to the development of distinctly individualized mineral forms. Other lithologists have used this word with different shades of meaning. Rosenbusch defines it as follows: “This substance, which is distinguished from micro- and crypto-crystalline aggregates by the absence of any action on polarized light, and from what may properly be called glass by not being entirely without structure and by being decidedly less transparent, I call microfelsite or the microfelsitic base.”