What are the two main groups of rock-forming minerals?

• A. Silicates and Non-Silicates
• B. Oxides and Sulfides
• C. Halides and Carbonates
• D. Phosphates and Sulfides

Answer: (A)

The main idea here is how rock-forming minerals are broadly categorized. Most of Earth’s crust is made up of silicate minerals, which are built from silicon–oxygen tetrahedra that can link in various ways to form a huge variety of minerals like quartz, feldspars, micas, and the pyroxenes and amphiboles, as well as olivine. This structural versatility and the abundance of silicon and oxygen give silicates dominance in rocks.

The other broad group is non-silicate minerals, which includes all minerals that do not contain those silicon–oxygen tetrahedra. This covers oxide minerals (such as hematite and magnetite), carbonates (like calcite and dolomite), sulfates (like gypsum), halides (like halite), sulfides (like pyrite), and phosphates (like apatite). They’re important and common in some rocks and ore deposits, but they’re far less abundant overall than silicates in the crust.

So the two main groups are silicate minerals and non-silicate minerals.