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| a mineral that is a complex borosilicate and hydroxide of aluminum containing iron and magnesium and calcium and lithium and sodium; it is usually black but occurs in transparent colored forms that are used as gemstones | |||
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| any of a class of drugs that block the flow of the electrolyte calcium (either in nerve cell conduction or smooth muscle contraction of the heart); has been used in the treatment of angina or arrhythmia or hypertension or migraine |