Melaphyre

• Webster's Revised Unabridged Dictionary
  • n Melaphyre (Min) Any one of several dark-colored augitic, eruptive rocks allied to basalt.
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• • n melaphyre A fine-grained greenish- or brownish-black aggregate of plagioclase, augite, olivin, magnetite, or titaniferous iron and some chloritic mineral, usually delessite. The term melaphyre, as it has been formerly used by lithologists, includes a considerable variety of rocks; but, as now generally restricted, it is properly applied to such basalts as have undergone considerable alteration. Hence the melaphyres are, in point of fact, mostly of Paleozoic age, although some are Mesozoic, because the older a rock is, other things being equal, the more likely it is to have undergone chemical change.
  • n melaphyre It is proposed, in the field classification accompanying the quantitative system of classification of igneous rocks (see rock), to restore the term melaphyre to its early significance and apply it to all dark-colored porphyries, of any composition.
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• • ns Melaphyre a pre-Tertiary basalt, usually altered
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