Why are granitic igneous rocks light in color?

Question

Why are granitic igneous rocks light in color?

Answer 1

It is all in the chemical composition of granite.

Granite consists of at least 10% visble quartz, one or more Feldspars and small amounts of accessory minerals mainly micas.

Quartz is glassy and colourless to pearly white. Felspars range from off white through light greys to pinks (rarely greens, or blues, but not usually in granites) Muscovite Mica is glittering metalic silver (usually as small flecks) while Biotite is usually dark to black.

As the main constituents of granite are light coloured then granites are typically light to medium grey or pinkish in colour.

It is the more basic rocks with a higher proportion of ferromagnesian minerals that mtend to be dark in colour