Concrete contains two nonmetallic mineral resources: ______ and ______.

• A. Limestone and Clay
• B. Quartz and Feldspar
• C. Sand and Gravel
• D. Gypsum and Anhydrite

Answer: (C)

Concrete is built from a cement paste plus aggregates, so the two nonmetallic mineral resources that form its bulk are the aggregates: sand for the fine portion and gravel for the coarse portion. These nonmetallic minerals provide most of the volume and the strength of the concrete. Limestone and clay are primarily used to make cement itself, not the aggregate that goes into the concrete mix. Quartz and feldspar are minerals used in other industries like glass and ceramics, not the standard concrete components. Gypsum and anhydrite are associated with cement production to regulate setting time, rather than forming the main concrete mix. So the combination that fits the concrete mix is sand and gravel.