What would be the most likely mineral assemblage observed in a granite?

• A. Quartz, orthoclase, plagioclase, hornblende
• B. Calcite, dolomite, quartz, hematite
• C. Olivine, pyroxene, plagioclase, magnetite
• D. Biotite, quartz, feldspar, garnet

Answer: (A)

Granite is a felsic intrusive igneous rock, so its minerals are light-colored silicates with quartz and feldspars making up the bulk, plus minor ferromagnesian minerals. The typical assemblage includes quartz and both feldspars—potassium feldspar (orthoclase) and plagioclase—often with a small amount of hornblende. This combination of quartz, orthoclase, plagioclase, and hornblende is a classic granite makeup: quartz provides durability and a glassy, translucent component; orthoclase and plagioclase together supply the feldspar framework; hornblende adds the common amphibole in many granites. The other options mix minerals not characteristic of granite—carbonates like calcite and dolomite point to carbonate rocks, olivine and pyroxene indicate mafic rocks, and garnet is not a defining, universal granite mineral.