Item talk:Q161240
From geokb
Geoscience Ontology Description
Leucocratic phaneritic crystalline igneous rock consisting essentially of plagioclase, often with small amounts of pyroxene. By definition, colour index M is less than 10, and plagiclase to total feldspar ratio is greater than 0.9. Less than 20 percent quartz and less than 10 percent feldspathoid in the QAPF fraction. QAPF field 10, 10*, and 10'. Anorthositic rock term invented to label the combined QAPF fields 10, 10*, and 10', in order to construct hierarchy in this vocabulary.
