Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks.
Petrographic examination is required for identification of specific types of granitoids.
The radiation causes charge to remain within the grains in structurally unstable "electron traps".
Luminescence dating refers to a group of methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating.
It is useful to geologists and archaeologists who want to know when such an event occurred.
Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic.
A granitic rock with a porphyritic texture is known as a granite porphyry.