| 31. | Orthoclase feldspar ( KAlSi 3 O 8 ) is a mineral commonly found in granite, a plutonic igneous rock.
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| 32. | Cryptoperthite textures form when orthoclase ( a feldspar mineral containing both potassium and sodium cations ) is quenched very rapidly.
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| 33. | Ostwald ripening is thought to occur in the formation of orthoclase megacrysts in granites as a consequence of subsolidus growth.
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| 34. | Adjacent to the hotel the granite is coarse-grained with large phenocrysts of orthoclase, sometimes more than in length.
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| 35. | They consist of quartz, plagioclase, orthoclase or alkali feldspar, rare mafics ( pyroxene ), and rare zircon.
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| 36. | About 25 % of the volcanics contain crystal content, including plagioclase, hornblende, orthopyroxene, orthoclase and sporadic quartz.
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| 37. | If a rock undergoes phyllic alteration, then orthoclase feldspar, biotite and various silicates are altered in addition to plagioclase.
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| 38. | When a granitoid contains less than 10 % orthoclase, it is called tonalite; pyroxene and amphibole are common in tonalite.
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| 39. | In the acid rocks the common feldspars are orthoclase, perthite, microcline, and oligoclase all having much silica and alkalis.
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| 40. | While slowly cooling within the earth, sodium-rich albite lamellae form by exsolution, enriching the remaining orthoclase with potassium.
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