from The Century Dictionary and Cyclopedia
- In petrography, noting a porphyry containing phenocrysts of both alferric silicates (hornblende, augite, biotite) and the simpler ferric or ferromagnesian minerals (hypersthene, diopside, olivin): proposed by Cross, Iddings, Pirsson, and Washington (1902) in their quantitative classification of igneous rocks (which see, under rock).
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