Rocks & Minerals — Set 1

Correct Answer: B. Petrology

Petrology is the branch of geology that studies rocks and the conditions under which they form. It involves the analysis of the origin, composition, and structure of rocks. The term is derived from the Greek word 'petra' meaning rock.

Correct Answer: D. Igneous Rocks

Igneous rocks are formed when molten rock cools and solidifies. They are often called primary rocks because other rock types are derived from them. Examples include granite and basalt.

Correct Answer: A. Granite

Granite forms when magma cools slowly beneath the Earth's surface. This slow cooling allows large crystals to form, giving it a coarse texture. It is widely used in construction due to its hardness.

Correct Answer: B. Extrusive Igneous

Basalt is an extrusive igneous rock formed from the rapid cooling of lava on the surface. It has a fine-grained texture because crystals do not have time to grow large. It is the most common rock type in the Earth's oceanic crust.

Correct Answer: D. Sedimentary Rocks

Fossils are preserved in sedimentary rocks because these rocks form at temperatures and pressures that do not destroy remains. Organisms get buried in layers of sediment which eventually harden into rock. Igneous and metamorphic processes usually destroy organic material.

Correct Answer: A. Limestone

Marble is formed when limestone is subjected to intense heat and pressure. This process recrystallizes the calcite minerals in the limestone. Pure marble is typically white, but impurities can give it various colors.

Correct Answer: A. Quartzite

When sandstone is subjected to heat and pressure, it metamorphoses into quartzite. The quartz grains in the sandstone fuse together to form a very hard, durable rock. Quartzite breaks through the grains rather than around them.

Correct Answer: B. Slate

Shale transforms into slate under low-grade metamorphic conditions. Slate is fine-grained and splits easily into thin, flat sheets. It is commonly used for roofing and flooring.

Correct Answer: B. Sedimentary

Coal is an organic sedimentary rock formed from accumulated plant debris. Over millions of years, pressure and heat convert this plant matter into coal. It is a major source of energy worldwide.

Correct Answer: A. Talc

Talc is the softest mineral on the Mohs hardness scale with a rating of 1. It can be easily scratched by a fingernail. It is often used in cosmetic products like baby powder.