Which three minerals are usually found in granite?

(1) biotite, olivine, and hornblende

(2) quartz, pyroxene, and olivine

(3) potassium feldspar, quartz, and hornblende

(4) plagioclase feldspar, biotite, and pyroxene

The answer is (3). The big two giveaways are quartz and feldspar. If you live in Southern California for example, the beach sand are basically whiteish, slight pink with some dark spots, which are the quartz and feldspar hornblende and epidote. That's how you know the mountains are made of granite!