volatile fluxes

The volatile constituents of a magma.

volatile matter

In coal, those substances, other than moisture, that are given off as gas
and vapor during combustion. Standardized laboratory methods are used in
analysis. Syn:volatiles; volatile combustibles. AGI

volatile ratio

In coal, the ratio of the volatile matter to the sum of the volatile
matter and the fixed carbon. Federal Mine Safety

volatiles

The volatile constituents (or rest magma) remaining after the less
volatile ores have crystallized as igneous rocks. Syn:volatile matter
AGI

volborthite

A monoclinic mineral, Cu₃ V₂ O₇ (OH)₂ .2H (sub
2) O ; radioactive; has one perfect cleavage; dark olive to yellow-green;
a secondary mineral with carnotite in sandstone. Syn:uzbekite

volcanic

Characteristic of, pertaining to, situated in or upon, formed in, or
derived from volcanoes. See also:extrusive

volcanic ash

See:ash

volcanic breccia

a. A pyroclastic rock that consists of angular volcanic fragments that are
larger than 64 mm in diameter and that may or may not have a matrix.
AGI
b. A rock that is composed of accidental or nonvolcanic fragments in a
volcanic matrix. Syn:alloclastic breccia; lava breccia. AGI

volcanic clay

See:bentonite

volcanic conglomerate

A water-deposited conglomerate containing more than 50% volcanic material,
esp. coarse pyroclastics. AGI

volcanic dust

See:ash

volcanic earthquake

A seismic disturbance that is due to the direct action of volcanic force,
or one whose origin lies under or near a volcano, whether active, dormant,
or extinct. AGI

volcanic focus

The subterranean seat or center of volcanism of a region or of a volcano.
AGI

volcanic glass

A natural glass produced by the cooling of molten lava, or a liquid
fraction of it, too rapidly to permit crystallization. Examples are
obsidian, pitchstone, tachylyte, and the glassy mesostasis of many
extrusive rocks. CF:glass

volcanicity

See:volcanism

volcanic ore deposits

The major group of ore deposits of magmatic origin, designated as young by
European mineralogists, which have been formed under near-surface
conditions and very often in Tertiary or younger volcanic rocks. In a
strict sense, deposits formed in relation to surface eruptions.
Schieferdecker

volcanic plain

Surface formed by extensive lava or ash flows that cover topographic
irregularities. AGI

volcanic rift zone

See:rift zone

volcanic rock

a. A generally finely crystalline or glassy igneous rock resulting from
volcanic action at or near the Earth's surface, either ejected explosively
or extruded as lava; e.g., basalt. The term includes near-surface
intrusions that form a part of the volcanic structure. Syn:volcanite
AGI
b. A general term to include the effusive rocks and associated high-level
intrusive rocks; they are dominantly basic. AGI

volcanics

A general collective term for extrusive igneous and pyroclastic material
and rocks.

volcanic water

Water in, or derived from, magma at the Earth's surface or at a relatively
shallow level; juvenile water of volcanic origin. AGI