Poikilitic texture refers to igneous rocks where large later-formed less perfect crystals ('oikocrysts') surround smaller early-formed idiomorphic crystals ('chadacrysts') of other minerals.[1] A poikilitic texture is most easily observed in petrographic thin sections.It is very characteristic of many diabases, in which large crystals of augite enclose smaller laths of plagioclase feldspar.Biotite and hornblende frequently enclose feldspar ophitically; less commonly iron oxides and sphene do so.In peridotites the "lustre-mottled" structure arises from pyroxene or hornblende enveloping olivine in the same manner.
Ophitic texture between an
augite
(blue-green) oikocryst surrounding smaller
plagioclase
(black and white) chadacrysts
