Definition
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Etymology
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Hyaloclastite is an aggregate of fine, glassy debris formed by the sudden contact of hot, coherent magma and cold water or water-saturated sediment
Fine Grained Rock, Opaque Rock
Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite).
from French néphéline, from Greek nephelē
Fine Grained Rock, Opaque Rock