Question

Question 8 :
A student analyzing an unknown rock that formed on Earth's surface observes that the rock has no layers, no
individual particles or crystal grains, and is smooth and glassy. The student will classify the rock as:-​

Answer 1

Answer:

intrusive igneous rock.

extrusive igneous rock.

intrusive metamorphic rock.

extrusive metamorphic rock.

Answer 2

The rocks can be obsidian or pumice rocks, which are igneous. Igneous rocks have no layers in them.

• Obsidian is an igneous rock with no layers. This rock is formed when lava cools quickly above ground and as a result, crystal grain or individual particles do not get formed. Smoothness, glassy, and uniform structure are the characteristics of these volcanic rocks that get formed near active volcanoes. Obsidian is commonly used as a gemstone in jewelry.
• Pumice is an extrusive igneous rock that is formed outside of the volcano due to volcanic eruptions. The main characteristic of this rock is that it is so light that it can actually float in water. Also, Pumice is a kind of glass with no mineral compositions. It is primarily used as a decorative stone.

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