A crystal having two of the three axes inclined to the third and
perpendicular to each other. Standard, 2
a. The name applied to commercial mixtures of rare-earth elements obtained
from monazite sand by extraction followed by the elimination of cerium and
thorium from the mixture. The name is used like that of an element in
naming mixed oxides and salts. The approximate composition of didymium
from monazite, expressed as rare-earth oxides, is 46% lanthana, La2
O3 ; 10% praseodymia, Pr6 O11 ; 32% neodymia, Nd (sub
2) O3 ; 5% samaria, Sm2 O3 ; 0.4% yttrium earth
oxides; 1% ceria, CeO2 ; 3% gadolinia, Gd2 O3 ; and
2% others. The mineral bastnaesite could also be a source of didymium
mixtures. CCD, 2
b. The name didymium has also been applied to mixtures of the elements
praseodymium and neodymium because such mixtures were once thought to be
an element; it was assigned the symbol, Di. CCD, 2
A former name for a plagioclase mineral.
a. See:bell tap
b. A piece of hard iron, placed in a mortar to receive the blow of a stamp
or in a pan to receive the friction of a muller as ore is crushed between
the die and the stamp or muller. Fay
Alloys that are suitable for die casting and that can be relied on for
accuracy and resistance to corrosion when cast. Aluminum-, copper-, tin-,
zinc-, and lead-base alloys are those generally used. CTD
See:bell tap
a. A material that offers relatively high resistance to the passage of an
electric current but through which magnetic or electrostatic lines of
force may pass. Most insulating materials, for example, air, porcelain,
mica, and glass, are dielectrics; and a perfect vacuum would constitute a
perfect dielectric. NCB
b. An insulator. A term applied to the insulating material between the
plates of a capacitor. Hunt
The numerical expressions of the resistance to the passage of an electric
current between two charged poles. It is the ratio of the attraction of
two oppositely charged poles as measured in a vacuum to their attraction
in a substance. The dielectric constant, which corresponds to permeability
in magnetic materials, is a measure of the polarizability of a material in
an electric field. This property determines the effective capacitance of a
rock material and consequently its static response to any applied electric
field, either direct or alternating. The dielectric constant of a vacuum
is unity. Hess; Dobrin
A method of high-frequency heating in which the object to be heated, which
must be nonconducting, is placed in a high-frequency alternating field
where it is heated by the continually reversed polarization of the
molecules. Applied in the foundry for drying sand cores. Osborne
Method of ore treatment based on differences between dielectric constants
of minerals suspended in an intermediate nonconducting fluid, when
subjected to electric fields. Of limited use in laboratory work.
Pryor, 1
The maximum potential gradient that a dielectric material can withstand
without rupture. Lowenheim
An isometric mineral, Ni3 As ; in gray-white cubes at Radstadt,
Salzburg, Austria.
See:bell tap
A pile driving drophammer operated by a type of diesel engine.
Hammond
In a compressor, explosions of mixtures of air and lubricating oil in the
compression chambers or other parts of the air system. Nichols, 1
a. Exhaust material, excluding water, that results from the incomplete
combustion of fuel and lubricating oil in a diesel engine. The
particulates collected on a filter after dilution of the exhaust with
ambient air, are carbonaceous solid chain aggregates with adsorbed or
condensed organic compounds. SME, 1
b. The fumes (solid condensation particles) and adsorbed gases that are
emitted from a diesel engine as a result of the combustion of diesel fuel.
Abbrev. DPM. DPM is a complex mixture of chemical compounds, composed of
nonvolatile carbon, hundreds of thousands of different adsorbed or
condensed hydrocarbons, sulfates, and trace quantities of metallic
compounds. DPM is of special concern because it is almost entirely
respirable, with 90% of the particles, by mass, having an equivalent
aerodynamic diameter of less than 1.0 mu m. This means that the particles
can penetrate to the deepest regions of the lungs and, if retained, cause
or contribute to the development of lung disease. Of equal concern is the
ability of DPM to adsorb other chemical substances, such as (1)
potentially mutagenic or carcinogenic polynuclear aromatic hydrocarbons
(PAHs); (2) gases, such as sulfur dioxide and nitrogen dioxide; and (3)
sulfuric and nitric acids. DPM carries these substances into the lungs,
where they may be removed and transported by body fluids to other organs,
where they may cause damage.
Any drill machine powered by a diesel engine. Long
In opencast mining, a powerful and robust diesel-engined vehicle carrying
from a few to more than 100 cubic yards of earth or rock. Also used in
trackless transport in tristate mines. Pryor, 3
Steels of plain-carbon or alloy types; they must be of high quality, which
is usually attained by special methods of processing. Essentially, they
are steels used in making tools for cutting, machining, shearing,
stamping, punching, and chipping. USBM, 5
An apparatus for the direct reading of a Brinell hardness after impression
without the aid of magnification or conversion tables. Osborne
A monoclinic mineral, Ca2 (IO3 )2 (CrO4 ) ;
dark golden-yellow; forms prismatic, tabular, fibrous, or columnar
crystals; at Atacama, Peru.