from The Century Dictionary and Cyclopedia

  • n. In petrography, in the quantitative system of classification, the name of the third class of igneous rocks, which contain equal or nearly equal amounts of salic minerals (normative quartz, feldspars, feldspathoids, corundum, or zircon) and femic minerals (normative ferromagnesian and other minerals), that is, within the ratio . See rock.


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