Of a mineral: older than the rock or deposit of which it forms part. Contrasted with "authigenic".
Late 19th century; earliest use found in Frederick Hatch (1864–1932), geologist and mining engineer. From German allothigen (E. Kalkowsky 1880, in Neues Jahrb. f. Mineralogie 1 4; from ancient Greek ἄλλοθι elsewhere (from ἄλλος other + -θι, suffix forming adverbs) + German -gen see -genic) + -ic.