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To form vesicles in, as lava.

d by the heat of a volcano. Volcanic bomb, a mass ejected from a volcano, often of molten lava having a rounded form. -- Volcanic cone, a hill, conical in form, built up of cinders, tufa, or lava, during volcanic eruptions. -- Volcanic foci, the subterranean centers of volcanic action; the points beneath volcanoes wh…

A column of igneous rock formed by congelation of lava in the conduit of a volcano and later exposed by the removal of surrounding rocks.

iated with a volcanic outburst and due to the eruption or to convection currents over hot lava.

A mountain or hill, usually more or less conical in form, from which lava, cinders, steam, sulphur gases, and the like, are ejected; -- often popularly called a burning mountain.

thers. These species occur of secondary origin in the cavities of amygdaloid, basalt, and lava, also, less frequently, in granite and gneiss. So called because many of these species intumesce before the blowpipe. Needle zeolite, needlestone; natrolite.