antiperthite

mineral

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June 18, 2026

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Antiperthite is a type of feldspar rock composed of plagioclase feldspar that contains lamellae (thin layers) of orthoclase feldspar. This is essentially the inverse of perthite, which consists of sodium-rich albite intergrown with potassium-rich feldspar.12

The term "antiperthite" is derived from "anti-" meaning opposite, and "perthite". Perthite itself was initially believed to be a single mineral, named after a location near Perth, Ontario. The formation of perthite involves the slow cooling of a molten mixture of sodium and potassium feldspar, leading to the separation of the two distinct feldspar phases.21

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feldspar
Chemical composition
…over the plagioclase constituent, whereas antiperthite is the name given to intimate mixtures in which the plagioclase constituent is predominant. Perthites are common, whereas antiperthites are relatively rare.
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…over the plagioclase constituent, whereas antiperthite is the name given to intimate mixtures in which the plagioclase constituent is predominant. Perthites are common, whereas antiperthites are relatively rare.
Read More