blasto- A prefix applied to textural terms and used to indicate the partial or complete replacement of a textural element in the original rock by crystals which have grown during metamorphic recrystallization. For example, the term ‘blastoporphyritic’ refers to a porphyritic igneous rock (see PORPHYRY) which has undergone metamorphism, and in which the phenocrysts remain as recognizable textural relicts even though each has been replaced by an aggregate of new metamorphic minerals.

blasto- combining form denoting a germ cell or embryo.