Which of the following are the two main constituents of granite?

Granite is a plutonic igneous rock primarily composed of quartz and feldspar. Chemically, it is classified as an acidic rock due to its high silica (SiO2) content, which typically ranges from 70% to 77% by weight [1]. The second most significant chemical component is alumina (Al2O3), derived from its high feldspar content. Feldspar itself is a mineral group where the main constituents include silicon and aluminium, along with potassium, sodium, or calcium [2]. While granite contains minor amounts of iron, magnesium, and potassium oxides, its defining chemical profile is dominated by silica and aluminium [1]. This composition makes granite less dense and lighter in color compared to basic rocks [1]. Therefore, silica and aluminium are the two main chemical constituents that characterize the rock's overall makeup.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 13: Types of Rocks & Rock Cycle > Acid Rocks > p. 170
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 13: Types of Rocks & Rock Cycle > 13.5. Some Rock-Forming Minerals > p. 175