albite twin

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The plagioclase feldspars, particularly albite (NaAlSi3O8), are frequently twinned on the albite law (see twin law) where the twin plane and composition plane is (010). This twinning is often repeated to give a series of fine lamellae, seen in the hand specimens as striations (particularly on the basal plane); such twinning is usually called ‘polysynthetic’ or ‘lamellar’ twinning.

Subjects: Earth Sciences and Geography.

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