Granite & Pegmatite

Both granite and pegmatite are made from the same minerals (pink zone in chart). These are silicates including potassium and plagioclase feldspars, quartz, biotite and amphibole. Both are intrusive igneous rocks meaning that the magma from which they formed never reached the earth's surface. Instead it cooled slowly, sometimes very slowly underground. This slow cooling process together with other factors gave the crystal grains in these rocks time to grow to very large sizes.

These large crystals give the rock coarse (granite) to very coarse (pegmatite) texture. Granite typically has crystals of from 1 to 10 mm in size while pegmatite's crystals can be 10mm (1cm) and very much larger (see ESRT). They are non-vesicular (no gas pockets).

Both are FELSIC and low density. Granite makes up much of the crust beneath the continents. 

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