Slang term for a safety hat. BCI
a. A hard knob or knot formed by extreme cementation of sandstone.
b. A large, smooth rounded stone found esp. in coarse gravel.
c. A tunnel in a coal mine driven through rock. Syn:hard heading
d. A hard, brittle, white residue obtained in refining tin by liquation,
containing, among other things, tin, iron, arsenic, and copper. Also, a
refractory lump or ore only partly smelted. ASM, 1
A heading driven in rock. In S. Wales and elsewhere, men employed in hard
headings have suffered greatly from silicosis. Syn:hardhead
See also:stone drift
Cylindroconical ball mill, made in three sections--a flattish cone at feed
end followed by a cylindrical drum, and finishing with a steep cone
leading to the discharge trunnion. The tricone mill has wedge-shaped
liners in the drum section that turn this into a gentle conic frustrum
widest at the feed end. Pryor, 3
A machine for removing the maximum amount of liquid from a mixture of
liquid and finally divided solids. The solids settle out on the bottom of
the thickener tank as a sludge, and the clear liquid overflows at the top
of the tank. It is used for processing chemical, metallurgical, and
coal-washing slurries. Nelson
A muffle kiln fired at a temperature between that of enamel and gloss
kilns. CTD
Mica that, when slightly flexed or distorted with thumb pressure,
generally does not show any tendency to delaminate. Such mica, in thick
pieces, will give an almost metallic sound when tapped or dropped on a
hard surface. Skow
A term applied in the grading of quartz crystals to fairly large
needlelike inclusions or imperfections that appear to be hard.
Am. Mineral., 2
a. Quality of water based on the presence of dissolved calcium or
magnesium. See also:hard water
b. As used by individuals associated with the drilling and bit-setting
industry, the relative ability of a mineral to scratch another mineral or
to be penetrated by a Knoop indenter. See also:hardness test
Long
c. Of a brittle mineral, the resistance to scratching or abrasion by
another mineral, e.g., the Mohs scale of relative hardness, which ranges
from 1 (talc) to 10 (diamond), or the Povarennykh scale from 1 (talc
[001]) to 15 (bort diamond [111]). See also:hardness scale
d. Resistance of a metal to plastic deformation by indentors of various
shapes as defined by the Brinell, Knoop, Rockwell, and Vickers scales.
See:hardness points
See:hardness points
A series of small pieces of minerals of differing hardness, polished flat,
and set side by side in cement, for testing hardness of another mineral,
which is drawn across one piece after another, beginning with the hardest,
until it scratches one.
Small pieces of minerals of differing hardness, with one end pointed and
affixed to small handles of wood, metal, or plastic, to be held in hand
and used for testing hardness of another mineral, by ascertaining which
points will scratch it. Minerals of hardness 6 to 10 are usually used as
points for testing gem stones. Syn:hardness gage; hardness pencils.
a. The scale by which the hardness of a mineral is determined as compared
with a standard. The Mohs scale is as follows: talc, gypsum, calcite,
fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond. Also
called Mohs scale. See also:hard; hardness; hardness test. Fay
b. Quantitative units by means of which the relative hardness of minerals
and metals can be determined, which for convenience is expressed in Mohs,
Knoop, or scleroscope units for minerals and Vickers, Brinell, or Rockwell
units for metals. Long
Any listing of substances as to their comparative hardness.
A determination of the relative hardness of a mineral, such as scratch
hardness, as made on a specimen, using appropriate hardness-testing
apparatus and techniques. See also:hardness; hardness scale.
Long
A hand instrument in which hardness points are set as equidistant spokes
of a rimless wheel, permitting a more rapid selection of points in testing
hardness.
a. A layer of gravel encountered in the digging of a gold placer,
occurring 1 to 2 m below the ground surface and partly cemented with
limonite. AGI
b. A popular term used loosely to designate any relatively hard layer that
is difficult to excavate or drill; e.g., a thin resistant layer of
limestone interbedded with easily drilled soft shales. AGI
c. See:caliche
Ionizing radiation of short wavelength and high penetration. NCB
a. A term used loosely for igneous or metamorphic rock, as distinguished
from sedimentary rock. AGI
b. A rock that is relatively resistant to erosion. AGI
c. Rock that requires drilling and blasting for its economical removal.
CF:soft rock
Drilling done in dense and solid igneous or highly silicified rocks, which
can be penetrated economically only by diamond bits, as opposed to that
done in softer rocks easily cut by roller or wing-type rotary bits.
Long