A monoclinic mineral, KAl2 (Si3 Al)O10 (OH,F)2;
mica group; pseudohexagonal; perfect basal cleavage; forms large,
transparent, strong, electrically and thermally insulating, stable sheets;
a common rock-forming mineral in silicic plutonic rocks, mica schists,
gneisses, and commercially in pegmatites; also a hydrothermal and
weathering product of feldspar and in detrital sediments. Also spelled:
moscovite. Syn:isinglass; white mica; potash mica; common mica;
Muscovy glass; mirror stone. Sericite is fine-grained muscovite, commonly
in connection with hydrothermal alteration, but sericite also includes
paragonite and illite. Illite is a common syn. for fine-grained muscovite
in clay mineralogy.
See:muscovite
A standard form of coal cutter jib with a sprocket at the end remote from
the machine. The sprocket carries a vertical turret or bar and is driven
by the cutting chain. The bar makes a vertical cut at the back of the
normal horizontal cut. See also:turret jib
A bog, usually a sphagnum bog, frequently with grassy tussocks, growing in
wet, poorly drained boreal regions, often areas of permafrost. Tamarack
and black spruce are commonly associated with muskeg areas.
Syn:maskeeg
A band containing or chiefly composed of mussellike shells, very valuable
in the correlation of Coal Measures strata. Mason
A mixture of iron ore and fuel is reduced in an externally heated rotary
retort. The gases are exhausted and constitute the fuel when the process
has been started. The gases, after purification, are passed through
combustion rings surrounding the retort and are burned according to the
method of catalytic combustion. After reduction, the charge is cooled when
it is poured through a layer of fluxing material; it is then transferred
to a steelmaking furnace. Osborne
A spongy type of free gold found in the gossan above gold-silver-telluride
deposits. AGI
A soft corklike bitumen of porous or resinous consistency. Partly soluble
in organic solvents. Tomkeieff
A mineral, (Ag,Au)Te ; soft; heavy; gray-white; in tabular crystals with
perfect cleavage; an ore mineral.
A Malayan term denoting the degrees of fineness of gold.
A rock texture showing smooth, regular, curved contacts between minerals.
Schieferdecker
Abbrev. for medium-volatile bituminous.
See also:medium-volatile bituminous coal
A compact, chertlike rock without cleavage, but with a streaky or banded
structure, produced by the extreme granulation and shearing of rocks that
have been pulverized and rolled during overthrusting or intense dynamic
metamorphism. Mylonite may also be described as a microbreccia with flow
texture. See also:cataclasite; protomylonite; mylonite gneiss;
ultramylonite. AGI
A mylonitic rock that has been partly recrystallized.
See also:augen schist; cataclasite; flaser gabbro; mylonite;
phyllonite. AGI
Deformation of a rock by extreme microbrecciation, due to mechanical
forces applied in a definite direction, without noteworthy chemical
reconstitution of granulated minerals. Characteristically the mylonites
thus produced have a flinty, banded, or streaked appearance, and
undestroyed augen and lenses of the parent rock in a granulated matrix.
Also spelled mylonization. AGI
See:mylonitization
a. A white or gray chalcedony, opal, or massive quartz unevenly colored
by, or intergrown with, pink or reddish inclusions of cinnabar, the color
of which tends to become brown. The opal variety is know as opalite.
b. Cinnabar intergrown with common white opal or translucent chalcedony.
An intergrowth of plagioclase feldspar (commonly oligoclase) and
vermicular quartz, generally replacing potassium feldspar; formed during
the later stages of consolidation in an igneous rock or during a
subsequent period of plutonic activity. The quartz occurs as blobs.
See:vermicular quartz
Myrmekitelike intergrowth of predominant plagioclase and vermicular
orthoclase. The wormlike forms of orthoclase are, as a rule, broader than
those of quartz in the typical myrmekite. Schieferdecker
Myrmekitelike intergrowth of microcline and vermicular plagioclase.
Schieferdecker
A Diamond Core Drill Manufacturer's Association letter name for a range of
diamond drill fittings intended to be used together with the appropriate
casing having an inside diameter of 81 mm or somewhat less.
Cumming, 2