The exploitation of the economic concentrations of the heavy minerals
rutile, zircon, monazite, ilmenite, and sometimes gold, which occur in
sand dunes, beaches, coastal plains, and deposits located inland from the
shoreline. High-grade concentrate is usually obtained from low-grade
material by the use of suction dredges and spiral concentrators.
Nelson
See:beach placer
A placer deposit on a present or ancient sea beach. There may be a series
of paleo-beach placers owing to changes of shoreline.
See also:black sand; placer; beach concentrate. Syn:beach ore
A low, essentially continuous mound of beach or beach-and-dune material
(sand, gravel, shingle) heaped up by the action of waves and currents on
the backshore of a beach beyond the present limit of storm waves or the
reach of ordinary tides, and occurring singly or as one of a series of
approx. parallel deposits. The ridges are roughly parallel to the
shoreline and represent successive positions of an advancing shoreline.
AGI
a. The globule of precious metal obtained by the cupellation process in
assaying. Webster 3rd
b. In blowpipe analysis of minerals, a drop of a fused material, such as a
"borax bead," used as a solvent in color testing for various metals. The
addition of a metallic compound to the bead will cause the bead to assume
the color that is characteristic of the metal. See also:blowpiping
AGI
In ion exchange, sized resin spheres, usually +20 mesh, so constituted as
to capture ions from pregnant solutions under stated loading conditions
and to relinquish them under other (eluting) conditions. Two types are
anionic and cationic. See also:resin
In mineral identification, borax or other flux is fused to a transparent
bead by heating in a blowpipe or other flame in a small loop formed from
platinum wire. When suitable minerals are flux melted in this bead,
characteristic glassy colors are produced in an oxidizing or reducing
flame and serve to identify specific chemical elements.
A method of sizing finely ground, insoluble, homogeneous material or
classifying ore particles. A weighed quantity is dispersed in liquid and
allowed to settle for a timed period, a liquid fraction then being
decanted. The treatment is repeated several times, the settled fraction
now representing one size group (if homogeneous) or settled group (if
minerals of various densities are present). The decanted fluid is
similarly treated for progressively lengthened settling periods.
Pryor, 3
a. A bar or straight girder used to support a span of roof between two
support props or walls. See also:crossbar
b. The walking beam; a bar pivoted in the center, which rocks up and down,
actuating the tools in cable-tool drilling or the pumping rods in a well
being pumped. Hess
In crushing, seizure of rock slab between approaching jaws so as to
present crushing stress above unsupported parts of the rock, thus inducing
shear failure rather than failure under compression. Pryor, 3
A specially graduated arc attached to the vertical circle of an alidade or
transit to simplify the computation of elevation differences for inclined
stadia sights (without the use of vertical angles). The arc is so
graduated that each division on the arc is equal to 100 (0.5 sin 2A),
where A is the vertical angle. Named after William M. Beaman (1867-1937),
U.S. topographic engineer, who designed it in 1904. AGI
A process of rock bolting in flat-lying deposits where the bolts are
installed in bedded rock to bind the strata together to act as a single
beam capable of supporting itself and thus stabilizing the overlying rock.
Lewis
An instrument for describing large arcs. It consists of a beam of wood or
metal carrying two beam heads, adjustable for position along the beam, and
serving as the marking points of the compass. Syn:trammel
An early type of vertical steam engine. It operated the Cornish pump.
Nelson
A loose, coarse-grained pisolitic iron ore; limonite occurring in
lenticular aggregations. See also:pea ore
Shingle cemented by tufa, Ventnor, U.K.
A cleaned and screened anthracite product 7/8 in by 3/8 in (22.2 mm by 9.5
mm). Nelson
a. To bear in; underholing or undermining; driving in at the top or at the
side of a working.
b. Eng. A calcareous or clay ironstone nodule, Derbyshire. Arkell
c. The mass of iron, which, as a result of wear of the refractory
brickwork or blocks in the hearth bottom of a blast furnace, slowly
replaces much of the refractory material in this location.
Syn:salamander
Eng. A band of hard limestone consisting of numerous stromatoporoids,
mainly a ramose species, Wenlock Limestone, Dudley. Arkell
One of the bars that support the grate bars in a furnace. Fay
Heavy timbers placed in a shaft at intervals of 30 to 100 ft (9.1 to 30.5
m) to support shaft sets. They are usually put beneath the end plates and
dividers, and rest in hitches cut in the wall. Also used to support
pumping gear. Syn:biard