Eng. A variety of chalcedony of thin concentric layers, which, when cut
across, exhibit an iridescence resembling the colors of the rainbow.
Fay
See:iris quartz
A chamber in which fumes, such as those from molten metal, may be
condensed by a water shower. Standard, 2
A device used to measure precipitation (melted snow, sleet, or hail as
well as rain). It consists of a receiving funnel, a collecting vessel, and
a measuring cylinder. Syn:pluviometer; hyetometer; snow gage.
AGI
a. The washing-away of loose surface material by rainwater after it has
reached the ground but before it has been concentrated into definite
streams; specif. sheet erosion. Also, the movement downslope (under the
action of gravity) of material loosened by rainwater. It occurs esp. in
semiarid or scantily vegetated regions. AGI
b. The material that originates by the process of rainwash; material
transported and accumulated, or washed away, by rainwater. AGI
c. The rainwater involved in the process of rainwash. AGI
a. A vertical or inclined opening in a mine driven upward from a level to
connect with the level above, or to explore the ground for a limited
distance above one level. After two levels are connected, the connection
may be a winze or a raise, depending upon which level is taken as the
point of reference. Syn:raised shaft See also:raise borer
These machines are used to produce a circular excavation either between
two existing levels in an underground mine or between the surface and an
existing level in a mine. In raise boring, a pilothole is drilled down to
the lower level, the drillbit is removed and replaced by a reamer head
having a diameter with the same dimension as the desired excavation and
this head then is rotated and pulled back up towards the machine.
SME, 1
Equipment used in an opening (raise) that is mined upward. MSHA, 4
See:raise
Excavating a shaft or steep tunnel upward. See also:raise; rise.
Nelson
Mid. To split off the walls or sides of underground workings. Called rosh
in Leicestershire. Syn:rate
a. As used by diamond drillers and bit manufacturers, rake is the angle,
measured in degrees, formed by the leading face of a cutting tool and the
surface behind the cutting edge. See also:negative rake; positive rake.
Long
b. The inclination of anything from the vertical; said of mineral veins,
faults, etc. See also:pitch
c. A timber placed at an angle. See also:rakers
d. Shale containing ironstone nodules. BS, 11
A dozer blade or attachment made of spaced tines. Nichols, 1
A type of mechanical classifier utilizing reciprocal rakes on an inclined
plane to separate coarse from fine material contained in a water pulp,
overflowing the fine material and discharging the coarse material by means
of an inclined raking system.
Slanting props placed at the end of a drift set to keep the timbers steady
when blasts go off. See also:rake
Equipment for thickening in which the concentrated suspension settles in a
container of circular section and is delivered mechanically to one or more
discharge points by a series of arms revolving slowly around a central
shaft. BS, 5
a. A steeply inclined crosscutting irregular mineralized fracture or
fissure. BS, 11
b. Rake vein and gas vein are synonymous; it is said that they are lodes
filling distinct fissures. Their course in irregular; their dip, as a
rule, vertical. Ricketts
c. A vein or lode cutting through the strata.
A strut set at an angle to the vertical to support timbering during
excavation. Hammond
A method of boring somewhat similar to Fauck's. Hollow steel rods 2 in
(5.08 cm) in diameter are used with a mud flush. A walking beam, fitted
with steel springs, imparts from 80 to 120 short blows/min to the chisel.
Nelson
In 1909 Lord Raleigh established the general law of fluid flow: R = wV
2 (f)(wVD/m), where R = resistance of flow, w = density of fluid,
V = velocity of flow, D = diameter of pipe, m = viscosity of fluid, f =
signifies function. For any particular value of (wVD)/m, using any
combination of quantities, there will be a definite corresponding value of
R/wV2 . Lewis
An isometric mineral, Nax Mgx Al2-x (F,OH)6 .H
2 O ; structurally related to the pyrochlore group; occurs as
octahedra.