Rock-forming minerals are the primary minerals that constitute the Earth’s crust and are classified into different types based on their chemical composition and structure. Here are some key examples:
- Silicate Minerals:
- Quartz (SiO₂): Common in many rock types, such as granite and sandstone.
- Feldspar:
- Orthoclase (KAlSi₃O₈): A significant mineral in granite and other igneous rocks.
- Plagioclase (NaAlSi₃O₈ – CaAl₂Si₂O₈): Found in rocks like basalt, diorite, and gabbro.
- Mica:
- Muscovite (KAl₂(AlSi₃O₁₀)(OH)₂): Present in granite and schist, known for its shiny appearance and ability to split into thin layers.
- Biotite (K(Mg,Fe)₃(AlSi₃O₁₀)(OH)₂): Common in granite and metamorphic rocks such as schist.
- Amphibole:
- Hornblende: Found in both igneous and metamorphic rocks like basalt and schist.
- Pyroxene:
- Augite (Ca,Na)(Mg,Fe,Al)(Si,Al)₂O₆: Present in basalt and gabbro.
- Carbonate Minerals:
- Calcite (CaCO₃): A major component of limestone and marble.
- Dolomite (CaMg(CO₃)₂): Found in dolostone and marble.
- Oxide Minerals:
- Hematite (Fe₂O₃): Often seen in sedimentary rocks like iron-rich sandstone and some metamorphic rocks.
- Magnetite (Fe₃O₄): Found in igneous rocks such as basalt and gabbro.
- Sulphide Minerals:
- Pyrite (FeS₂): While not a primary rock-forming mineral, it can be present in certain sedimentary and metamorphic rocks.
These minerals are crucial to the composition of various rock types, including igneous, sedimentary, and metamorphic rocks. Their abundance and characteristics influence the properties of the rocks they are found in.