Produced by explosive or aerial ejection of ash, fragments, and glassy
material from a volcanic vent. Applied to the rocks and rock layers as
well as to the textures so formed. Stokes
A deposit made up mainly of rock material that has been expelled aerially,
normally explosively, from a volcanic vent, such as agglomerate, tuff, and
ash. The fragments range in size from bombs and blocks to dust or ash.
Such deposits are usually designated according to the lavas to which they
correspond in composition. Stokes
A broad term encompassing the intrusion and extrusion of magma and its
derivative. Adj. pyrogenic. AGI
A term introduced to designate minerals, such as olivine and chromite,
developed at high temperature in melts containing only a small proportion
of volatile (hyperfusible or fugitive) constituents.
See also:pyrogenic
Said of a process or of a deposit involving the intrusion and/or extrusion
of magma. See also:pyrogenetic; igneous. AGI
An ore mineral that crystallized as a primary magmatic mineral of igneous
rocks. Schieferdecker
A rock resulting from the cooling of a molten magma; an igneous rock.
The characteristics (such as the degree of fusibility or the flame
coloration) of a mineral observed by the use of the blowpipe.
Webster 3rd
An explosive resembling gunpowder in composition. Webster 2nd
A tetragonal mineral, MnO2 ; rutile group; trimorphous with
akhtenskite and ramsdellite; soft; metallic; steel gray; massive or
reniform; a source of manganese. CF:psilomelane
gray manganese ore.
Chemical decomposition by the action of heat.
Graphite formed by pyrolysis of a carbonaceous gas. Van Vlack
Metallurgy involved in winning and refining metals in which heat is used,
as in roasting and smelting. Practically all iron and steel, nickel and
tin, most copper, and a large proportion of zinc, gold, and silver, as
well as many of the minor metals, are won from their ores and concentrates
by pyrometallurgical methods. It is the most important and oldest class of
the extractive processes. ASM, 1
Metamorphism produced by heat; it is a local, intense type of thermal
metamorphism, resulting from unusually high temperatures at the contact of
a rock with magma, such as in xenoliths. CF:igneous metamorphism;
hydrometamorphism. See also:thermal metamorphism
Formed by metasomatic changes in rocks, principally in limestone, at or
near intrusive contacts, under the influence of magmatic emanations and
high to moderate temperature and pressure. AGI
Contact metamorphism. CF:metasomatism
An instrument that measures high temperature, e.g., of molten lavas, by
electrical or optical means. See also:optical pyrometer
A small, slender three-sided pyramid made of ceramic or refractory
material for use in determining the time-temperature effect of heating and
in obtaining the pyrometric cone equivalent (PCE) of refractory material.
Pyrometric cones are made in series, the temperature interval between
successive cones usually being 20 degrees C. The best known series are
Seger cones (Germany), Orton cones (United States), and Staffordshire
cones (United Kingdom). See also:cone; orton cone. ARI; Dodd
The number of that standard pyrometric cone whose tip would touch the
supporting plaque simultaneously with a cone of the refractory material
being investigated when tested in accordance with ASTM Test Method C-24.
Abbrev. PCE. ASTM
A hexagonal mineral, Pb5 (PO4 )3 Cl ; apatite group,
with iron replacing lead and arsenic replacing phosphorous; sp gr, 6 to 7;
in oxidized zones of lead-ore deposits. Syn:green lead ore
a. An isometric mineral, 8[Mg3 Al2 (SiO4 )3 ];
garnet group, with Fe and Mn replacing Mg and Cr replacing Al.
See also:pyralspite; pyralmandite. Crystallizes in dodecahedra and
trapezohedra; deep red to black; in high-pressure ultramafic and
metamorphic rocks; also in placers; a gemstone and an abrasive.
See also:Cape ruby; Bohemian garnet. Syn:rock ruby;
magnesium-aluminum garnet.
b. Formerly, a name for any bright red gem, such as ruby.