tephrine, tephrite

[Gr. tephra =cinders, Petrol.: A name originally given to a gray, ashlike rock of loose texture, the base of which was trachytic. Subsequent investigation has shown, however, that it consists of plagioclase felspar, a ociated with either nepheline or leucite, and sometimes with both, and also several acce ory minerals. This name has been until recently used by French geologists; but Rosenbusch ( Mikrosko pische Physiographie d. ma igen Gesteine, Stutt gart, 1877) has adopted it as a designation of a family" of rocks, most of which are equivalent to the phonolites (q. v.).