felsite
|fels-ite|
/ˈfɛlsaɪt/
light-colored fine-grained felsic rock
Etymology
'felsite' originates from German, specifically the word 'Felsit' (from 'Fels' meaning 'rock') combined with the suffix '-ite' (stone or rock).
'felsite' was adopted into English from the German term 'Felsit' in the 19th century and became the standard English geological term 'felsite' for fine-grained felsic rocks.
Initially used more broadly for light-colored or rock-like material ('rock'), the term evolved into a more specific geological meaning: a fine-grained, silica-rich (felsic) igneous rock.
Meanings by Part of Speech
Noun 1
a light-colored, fine-grained, siliceous (felsic) volcanic or hypabyssal rock composed mainly of quartz and feldspar; used as a general field term for fine-grained felsic igneous rocks.
Geologists collected a sample of felsite from the outcrop for thin-section analysis.
Synonyms
Noun 2
(Older/broader usage) Any fine-grained, light-colored igneous rock; sometimes used loosely for intrusive equivalents of fine-grained felsic rocks.
In older field reports the term felsite was sometimes applied to small-grained intrusive bodies.
Synonyms
Last updated: 2025/10/09 20:29