An orthorhombic mineral, Cu4 Al2 (SO4 )(OH)12
.2H2 O ; sky-blue to smalt-blue; minutely crystalline or
spheroidal. Formerly called lettsomite. Syn:velvet copper ore
Cycle of erosion. AGI
The complete series of changes or stages through which a landmass passes
from the inception of erosion on a newly uplifted or exposed surface
through its dissection into mountains and valleys to the final stage when
it is worn down to the level of the sea or to some other base level. The
cycle is usually subdivided into youthful, mature, and old-age stages. One
type or many types of erosion may be involved, and the landforms produced
and destroyed depend to a large extent on the climate, geographic
situation, and geologic structure of the landmass.
Syn:cycle of denudation; geographic cycle; geomorphic cycle.
Stokes
In mining operations, such as tunnel driving, shaft sinking, and coal
winning, there are certain tasks that must be repeated in cyclic fashion.
In tunnel driving, they are (1) drilling the round; (2) charging and
firing; (3) loading; and (4) supporting and track extension. This cycle of
operations is time analyzed to achieve maximum efficiency and speed.
Nelson
a. A sequence of related processes and conditions, repeated in the same
order, that is recorded in a sedimentary deposit. AGI
b. The deposition of sediments in a basin between the beginnings of two
successive marine transgressions, comprising the deposits formed initially
on dry land, followed by shallow-water and then deep-water deposits that
in turn gradually change to shallow-water and then dry-land type during a
marine regression. AGI
c. See:cyclothem; sedimentary cycle.
An instrumental phenomenon occurring in acoustic velocity logs. It
consists of intervals where the velocity recorded drops sharply to very
low values, and equally sharply, returns to a normal scale figure. Such a
log is spiky. Wyllie
The time required for the dipper of a mechanical shovel to push through
the bank and fill, swing to the haul unit, unload, and swing back to the
digging position. Cycle time is established under standard conditions of a
90 degrees angle of swing and with an optimum depth of cut.
Carson, 1
Adj. of cycle; recurrent rather than secular. AGI
A mining system in which each shift has a specific task to complete on the
conveyor face. If the task on any shift is not completed in time, the
following shifts are disorganized. In general, the face is machine cut
during the night shift; shot-firing and hand-filling of the coal occupy
the day shift; and the afternoon shift is responsible for moving the
conveyor and roof supports to the new line of face.
See also:conventional machine mining; conventional mining.
Nelson
In classification, periodic upset of correct separating density of pulp,
resulting in wrong release of oversize material from the closed grinding
circuit. Pryor, 3
In batch tests of small quantities of ore during development of a method
of concentration, the retention of selected fractions (usually middlings)
for admixture with fresh samples. Used to study effect of recycling
minerals or solutions, which they may have contaminated; also, to observe
effects of increased concentration of such compounds on the process as a
whole. See also:locked test
Repeated twinning of three or more individual crystals according to the
same twin law but with the twin axes or twin planes not parallel, commonly
resulting in threefold, fourfold, fivefold, sixfold, or eightfold twins,
which, if equally developed, display geometrical symmetry not found in
single crystals, e.g., chrysoberyl, rutile. CF:repeated twinning;
polysynthetic twinning.
The repeated twinning of three or more individuals according to the same
twin law but with the twinning axes not parallel. Often simulates a higher
order of symmetry than that of the untwinned crystal.
CF:polysynthetic twinning
a. The conical-shaped apparatus used in dust collecting operations and
fine grinding applications. In principle, the cyclone varies the speed of
air, which determines whether a given particle will drop through force of
specific gravity or be carried through friction of the air.
Enam. Dict.
b. A classifying (or concentrating) separator into which pulp is fed, so
as to take a circular path. Coarser and heavier fractions of solids report
at apex of long cone while finer particles overflow from central vortex.
Also called hydrocyclone. See also:cyclone washer;
centrifugal separation; centrifuge. Pryor, 4
Included angle of conical section of hydrocyclone. Pryor, 3
A device for classification by centrifugal means of fine particles
suspended in water, whereby the coarser grains collect at and are
discharged from the apex of the vessel, while the finer particles are
eliminated with the bulk of the water at the discharge orifice.
BS, 5
An apparatus for the separation by centrifugal means of fine particles
suspended in air or gas. BS, 5
A forced circulation heat treatment furnace designed to operate at a
maximum temperature of 760 degrees C, which is either gas fired or
electrically heated. The gas circulates at the rate of 0.89 m/s.
Osborne
A finer classified fraction, which leaves via the vortex finder of a
hydrocyclone. Pryor, 3
A funnel-shaped device for removing material from an airstream by
centrifugal force. ASM, 1