COLOUR INDEX


Meaning of COLOUR INDEX in English

In igneous petrology , the sum of the volume percentages of the coloured, or dark, minerals in the rock.

The most common light-coloured minerals are feldspars, feldspathoids, and silica or quartz; abundant dark-coloured minerals include olivine, pyroxene, amphibole, biotite, garnet, tourmaline, iron oxides, sulfides, and metals.

Britannica English dictionary.      Английский словарь Британика.