a. Deferred crystallization, which, in glassy igneous rocks, converts
obsidians and pitchstones into dull cryptocrystalline rocks (commonly
called felsites) consisting of minute grains of quartz and feldspar. Such
devitrified glasses reveal their originally vitreous nature by traces of
perlitic and spherulitic textures.
b. The process by which glassy rocks break down into definite minerals,
which are commonly minute, chiefly quartz and feldspar.
c. Any change from a glassy state to a crystalline state after
solidification.
d. In ceramics, a surface defect manifested by loss of gloss as a result
of crystallization.
To destroy the glasslike character of volcanic glasses by changing from
the vitreous state to the crystalline state.
Progressive loss of volatiles by the substance undergoing coalification
process. Tomkeieff
The fourth period, in order of decreasing age, of the periods making up
the Paleozoic era. It followed the Silurian period and was succeeded by
the Mississippian period. Also, the system of strata deposited at that
time. Sometimes called the Age of Fishes. Fay
The sink-float or dense-media process used for coal cleaning. The
separating fluid is a clay-barite water pulp. Pryor, 3
To remove water from a mine; an expression used in the industry in place
of the more technically correct word, unwater. Hudson
a. The removal of water from a drowned shaft or waterlogged workings by
pumping or drainage as a safety measure or as a preliminary step to
resumption of development in the area. CF:unwatering
b. The draining of an aquifer when adjacent wells or mine workings are
pumped.
c. The mechanical separation of a mixture of coal and water into two
parts, one which is relatively coal-free, the other relatively water-free,
with respect to the original mixture. Mitchell
d. The mechanical separation of solid matter from water in which it is
dispersed, by such equipment as thickeners, classifiers, hydrocyclones,
filters, and centrifuges. Coarser coal sizes may be dewatered by slotted
screens or perforated bucket elevators.
e. The process in which solid material, either submerged or containing
liquid, is conveyed or elevated in a manner that allows the liquid to
drain off while the solid material is in transit.
A settling tank for clarifying washer circulating water or for
concentrating gold slimes before cyaniding. The tank may have a
continuously working rake that moves the sludge toward the outlet pipe in
the bottom. See also:dryer
Similar to the continuous bucket elevator, it is often used in sand and
gravel plants where the dredge line discharges to a sump. The dewatering
elevator digs the material from the sump, allowing the water to drain out
through perforations in the backs of the buckets while being elevated, and
discharges to the plant for further processing. Pit and Quarry
A screen used for the separation of water from solids. BS, 5
A mixture of a disordered clinochrysotile or lizardite with a talclike
mineral.
An orthorhombic mineral, Pb3 (UO2 )6 H2 (PO
4 )4 O4 .12H2 O ; strongly radioactive; canary
yellow; associated with torbernite and other secondary uranium minerals.
The temperature to which air must be cooled, at constant pressure and
constant water vapor content, in order for saturation to occur. Since the
pressure of the water vapor content of the air becomes the saturation
pressure, the dewpoint may also be defined as the temperature at which the
saturation pressure is the same as the existing vapor pressure. Also
called saturation point. AGI
An instrument for determining the dewpoint; a type of hygrometer.
Hunt
A carbohydrate, C6 H18 O5 , hydrolyzed from starch by
dilute acids. Used in flotation as depressant. Pryor, 1
An etching reagent that reveals not only the macrostructure and faults,
such as piping, segregation, particularly sulfur and phosphorus, and
cracks, but also slip lines in mild steel that has been stressed beyond
its elastic limit. Composition is 100 mL of distilled water, 100 mL of
concentrated hydrochloric acid, and 40 g of crystallized chromic acid, 16
g of anhydrous nickel chloride. Osborne
A ferroan variety of clinchlore. Syn:destinezite
In the United States, an intrusive rock whose main components are
labradorite and pyroxene and that is characterized by ophitic texture. As
originally applied by Brongniart in 1807, the term corresponded to what is
now recognized as diorite. The word has come to mean a pre-Tertiary basalt
in Germany, a decomposed basalt in England, and a dike-rock with ophitic
texture in the United States and Canada (Johannsen, 1939). CF:trap
Syn:dolerite
Composed of or resembling diabase. AGI
Pertaining to a texture in metamorphic rock that consists of intricately
intergrown and interpenetrating constituents, usually with rodlike shapes.
AGI