Knowra Orthoclase Orthoclase Orthoclase is a potassium-rich feldspar mineral with formula KAlSi₃O₈. It is a common constituent of granitic rocks and a major mineral in the potassium feldspar group.
Feldspar : Feldspars are a family of abundant aluminosilicate minerals containing potassium, sodium, or calcium. Orthoclase belongs to this mineral family and shares its aluminosilicate framework.
Potassium feldspar : Potassium feldspar is the feldspar subgroup whose principal large cation is potassium. Orthoclase is one member of this compositionally defined subgroup.
Granite : Granite is a coarse-grained igneous rock composed mainly of quartz, feldspar, and smaller amounts of other minerals. Orthoclase is a common potassium feldspar in many granites.
Pikes Peak granite : Pikes Peak granite is a large, pink, Precambrian granite body in Colorado’s Front Range. Its abundant pink potassium feldspar includes conspicuous orthoclase.
Plagioclase : Plagioclase is a sodium–calcium feldspar series ranging from albite to anorthite. Its sodium–calcium chemistry contrasts with orthoclase’s potassium-rich composition.
Aluminosilicate : Aluminosilicates are minerals or materials in which aluminum and silicon form linked structures with oxygen. Its crystal framework is built from linked aluminum- and silicon-bearing tetrahedra.
Alkali feldspar : Alkali feldspars are potassium–sodium feldspars with compositions between potassium-rich and sodium-rich end members. Orthoclase can exchange potassium and sodium with related feldspars in this series.
Pegmatite : Pegmatite is an exceptionally coarse-grained igneous rock, commonly formed from late-stage, volatile-rich magma. Large orthoclase crystals can grow in potassium-rich pegmatites.
New York City pegmatite : New York City pegmatites are coarse-grained igneous bodies exposed in the region’s ancient metamorphic rocks. Some pegmatites in the region contain large potassium-feldspar crystals, including orthoclase.
Quartz : Quartz is crystalline silicon dioxide, a hard mineral common in igneous, sedimentary, and metamorphic rocks. Quartz commonly occurs beside orthoclase in granite but has different chemistry and cleavage.
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