Rocks & Minerals — Set 2
Geography · चट्टानें और खनिज · Questions 11–20 of 50
Which is the hardest natural mineral on the Mohs scale?
Correct Answer: B. Diamond
Diamond is the hardest known natural mineral, rating 10 on the Mohs scale. Its hardness is due to the strong covalent bonds between carbon atoms. Only a diamond can scratch another diamond.
What is the most abundant group of minerals in the Earth's crust?
Correct Answer: D. Feldspars
Feldspars make up about 60% of the Earth's crust, making them the most abundant mineral group. They are essential components of igneous, metamorphic, and sedimentary rocks. They typically contain silica and aluminum.
What is the chemical composition of the mineral Quartz?
Correct Answer: D. Silicon Dioxide (SiO2)
Quartz is composed of silicon dioxide, also known as silica. It is one of the most common and resistant minerals on Earth. Quartz is a major component of sand and granite.
Which igneous rock is known as 'volcanic glass' due to its lack of crystal structure?
Correct Answer: A. Obsidian
Obsidian forms when lava cools so rapidly that crystals do not have time to form. This results in a smooth, glass-like texture with sharp edges. Ancient cultures used it to make tools and weapons.
Which light-colored volcanic rock is known for being able to float on water?
Correct Answer: A. Pumice
Pumice is a volcanic rock that is extremely porous and full of gas bubbles. Its density is low enough that it can float on water. It forms during explosive volcanic eruptions.
Which sedimentary rock consists of rounded pebbles cemented together?
Correct Answer: B. Conglomerate
Conglomerate is a clastic sedimentary rock composed of rounded gravel or pebbles. The rounded shape indicates that the particles were transported a long distance by water. If the fragments are angular, the rock is called breccia.
What is molten rock called when it is beneath the Earth's surface?
Correct Answer: B. Magma
Molten rock located beneath the Earth's surface is called magma. It contains dissolved gases and crystals suspended in the melt. When magma erupts onto the surface, it is then called lava.
What is the term for molten rock that has erupted onto the Earth's surface?
Correct Answer: C. Lava
Once magma reaches the surface through a volcano or vent, it is called lava. As lava flows and cools, it loses dissolved gases. Solidified lava forms extrusive igneous rocks.
Which of the following represents a large, deep-seated intrusive igneous body?
Correct Answer: B. Batholith
A batholith is a massive body of intrusive igneous rock, usually granite, that covers a large area. They form deep underground and are exposed by erosion over millions of years. They are often the core of mountain ranges.
What is a vertical intrusion of magma that cuts across rock layers called?
Correct Answer: A. Dyke
A dyke is a sheet-like igneous intrusion that cuts vertically or steeply across existing rock layers. In contrast, a sill intrudes horizontally between layers. Dykes are often harder than the surrounding rock and stand out as walls.