The Earth's crust is primarily composed of eight major rock-forming minerals, often referred to as the "rock-forming" or "common" minerals. Here are five of them:
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Feldspar: This is the most abundant group of minerals in the Earth's crust, making up about 60% of it. It includes both plagioclase and orthoclase varieties.
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Quartz: Composed of silicon dioxide (SiO2), quartz is the second most abundant mineral in the Earth's crust and is known for its hardness and clarity.
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Mica: This group of minerals, which includes biotite and muscovite, is characterized by their sheet-like crystal structure and perfect cleavage.
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Amphibole: This group encompasses minerals like hornblende, which are typically found in igneous and metamorphic rocks. They have a double chain silicate structure.
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Pyroxene: Another important group of silicate minerals, pyroxenes are found in many igneous and metamorphic rocks. They have a single chain structure and are usually dark-colored.
These minerals are key contributors to the composition and classification of various rock types in the Earth's crust.