a. Heavy-media separation, or sink float. Separation of sinking heavy from
light floating mineral particles in fluid of intermediate density.
Abbreviation: DMS. See also:heavy-media separation
b. Separation of relatively light (floats) and heavy (sinks) particles, by
immersion in a bath of intermediate density. This is the dense or heavy
media, a finely ground slurry of appropriate heavy material in water.
Barite, magnetite ferrosilicon, and galena are in principal use.
A fluid formed by the artificial suspension in water of heavy particles
(e.g., magnetite, barite, and shale) that can be used in industry or in
the laboratory to divide coal into fractions of different specific
gravities. BS, 5
This method involves two essential features: (1) the circulation in the
jig of a middling of approx. 3/16 in (4.8 mm) or smaller in size, with sp
gr, 1.7 to 2.0--which fills the interstices of the jig bed and in effect
converts the jig into a float-and-sink machine; and (2) the use of a
suction stroke to hold the medium in the bed and prevent its washing over
with the coal. Mitchell
A process for the washing of coal, in which the desired separation is
effected in a dense medium. BS, 5
The collection, for reuse, of medium solids from dilute medium, usually
understood to include the removal, in whole or in part, of contaminating
fine coal and clay. Syn:medium-solids recovery
A machine for cleaning coal and other materials that uses a dense fluid in
which the coal floats and shale sinks. The fluid consists of water
intimately mixed with sand (or finely ground magnetite or even shale) and
agitated to maintain its consistency. The fluid has an effective specific
gravity of 1.3 to 1.9. In general, coal from about 8 in (20.3 cm) down to
1 in (2.54 cm) is washed by dense medium, below 1 in by Baum washer, and
below 0.75 mm (where cleaning is necessary) by froth flotation. Magnetite
as the dense medium solid is preferred as it can be easily recovered by
magnetic separators and also the upper limit of the specific gravity is
higher (up to 2.0). See also:coal-preparation plant; washery.
Nelson
This type of tonstein consists almost entirely of fine-grained kaolin
groundmass, showing weak aggregate polarization, containing isolated
corroded crystals of kaolinite. Such bands are commonly more than 100 mm
thick and light in color. IHCP
An apparatus used to determine the relative density, or specific gravity,
of a dense media.
An apparatus to obtain the specific gravity of pearls as an indication,
but not proof, of genuineness (cultured pearls tend to be denser).
An instrument for the measurement of the density of an image produced by
light, X-rays, gamma rays, etc., on a photographic plate; used in some
dust-sampling instruments. Nelson
a. The mass of a substance per unit volume. Webster 3rd
b. The quality or state of being dense; closeness of texture or
consistency. Webster 3rd
c. The distribution of a quantity (as mass, electricity, or energy) per
unit usually of space (as area, length, or volume). Webster 3rd
d. The ratio of the mass of any volume of a substance to the mass of an
equal volume of a standard substance; water is used as the standard
substance. Long
e. Having the quality of being dense, hard, or compact. Long
f. Weight of a substance in grams per cubic centimeter (at specified
temperature when close accuracy is needed). For liquids and solids, it
equals specific gravity. Density fluids are heavy liquids used in
float-sink tests. Of a particle, the true density is its mass (m) divided
by volume (v) excluding pores; its apparent density is its mass divided by
volume (m/v) including open but excluding closed pores. Of a mass of
particles (powder), the apparent density is mass divided by volume (m/v);
the bulk density mass divided by volume (m/v) under stated freely poured
conditions; and the tap density mass divided by volume (m/v) after
vibrating or tapping under stated conditions. See also:apparent density;
bulk density. Pryor, 3
g. Mass per unit volume. CF:specific gravity
h. Although density is defined as mass per unit volume, the term is
frequently used in place of unit weight in the field of soil mechanics.
See also:unit weight
The difference in density of a valuable mineral and the host rock.
Lewis
A current caused by differences in densities, for example, an excess of
evaporation, cooling, or dilution in a restricted basin or an open sea.
Schieferdecker
An instrument for direct measurement of formation densities in boreholes.
This tool furnishes a log of backscattered gamma radiation, which is a
simple function of formation density. Dobrin
The number of ounces of coal dust per cubic foot (or grams per cubic
meter) of space, suspended in the air or gases in a specified zone.
Rice, 2
The vapor density of a gas, or its density relative to hydrogen, is the
number of times a volume of the gas is heavier than the same volume of
hydrogen, the volume of both gases being at the same temperature and
pressure. Cooper
a. An indication of the spacing of seams in the strata; the seam density
is said to be high if the seams are close together, or low if they are
widely separated. BS, 7
b. The ratio of the sum of the thickness of a number of adjacent seams to
the thickness of an arbitrarily chosen sequence of strata. BS, 7
In powder metallurgy, the ratio of the determined density of a compact to
the absolute density of metal of the same composition, usually expressed
as a percentage. ASM, 1
A controlled blasting technique used to minimize damage, in which the
blasting of small, specially designed rounds over partial faces is used in
extremely sensitive situations. SME, 1
The act or process of filling cracks, crevices, or caverns encountered in
drilling a borehole with cement or grout; also, the cracks, etc., so
filled. Long
The sum of the processes that result in the wearing down of the surface of
the Earth, including wear by running water, solution, and wind action.