Which mineral is commonly an accessory mineral in granite?

• A. Biotite
• B. Calcite
• C. Halite
• D. Gypsum

Answer: (A)

Granite is built mainly from quartz and feldspar, but it also contains smaller amounts of other minerals that don’t define the rock’s name—these are accessory minerals. Biotite, a dark mica, commonly occurs in granitic rocks as small flakes mingling with the main minerals. Its presence is typical and helpful for identifying granitic textures, yet it doesn’t dominate the mineralogy the way quartz or feldspar do.

Calcite, halite, and gypsum are not characteristic accessory minerals of granite. Calcite is typical of carbonate rocks (or can appear as alteration products), while halite and gypsum are evaporites associated with desert or evaporite environments, not with granitic rocks.

So, the mineral commonly an accessory mineral in granite is biotite.