idiomorphic
/ˌɪdɪə(ʊ)ˈmɔːfɪk/Mineralogy
adjective
Of a mineral constituent in a rock: having its own characteristic crystal form.
Origin
Late 19th century; earliest use found in Geological Magazine. From idio- + -morphic, after German idiomorph or its apparent model French idiomorphe. Compare Hellenistic Greek ιδιόμορϕος of peculiar form.