Min. [f. fels (in felspar FELDSPAR) + -ITE.
The name was given by Kirwan himself (not by Widenmann as his language might seem to imply), and its form is due to his erroneous explanation of feldspath (see FELDSPAR).]
= FELSTONE.
1794. Kirwan, Min., I. 326. Felsite, or compact Felspar of Widenmann.
1804. Edin. Rev., III. 310. Kirwan … has called a substance in question Felsite, and not compact fieldstone.
1868. Dana, Min., § 315 (1880), 352. Felsite … constitutes the base of albite porphyry.
1882. W. J. Harrison, in Knowledge, 6 Oct., 305. A cream-coloured felsite.
attrib., as in felsite porphyry (see quot.).
1877. Le Conte, Elem. Geol., II. (1879), 206. Felsite porphyry, which may be considered the type, consists of a grayish or reddish feldspathic mass, containing large crystals of lighter-colored and purer feldspar.
Hence Felsitic a., consisting of or containing felsite or felstone.
1879. Prof. Hughes, in Q. Jrnl. Geol. Soc., XXXV. 682. The Felsitic series, consisting chiefly of quartz felsites and probably also of volcanic origin.
1880. Rudler, in Encycl. Brit. (ed. 9), XI. 49/2, ‘Granite.’ Crystals of orthoclase disseminated through a felsitic matrix…. In these veins the granite is apt to change its mineralogical constitution, becoming either fine-grained or felsitic.
