a. In crystallography, the plane passing through the optical axis of a
crystal. Standard, 2
b. The optical indicatrix of a biaxial mineral is a triaxial ellipsoid
with semiaxes proportional to the refractive indices alpha, beta, and
gamma. A principal section is an ellipse containing any two of these
semiaxes. The indicatrix of a uniaxial mineral is an ellipsoid of
revolution; its principal sections contain the axis of revolution which is
proportional to the refractive index epsilon.
The stress normal to one of three mutually perpendicular planes that
intersect at a point in a body on which the shearing stress is zero.
ASM, 1
To determine the stress in a member due to a system of applied forces, the
system can be split up into several component forces and their moments and
reactions added in order to calculate the total stress. Hammond
A dense-media process in which large-size coal is separated from the
refuse in a flowing bed of small coal in a reciprocating launder. Refuse
sinks to the bottom. The small coal is screened from the coarse refuse and
returned to the head of the launder by a drag conveyor. The floating large
coal passes over skimmers in the trough to the discharge chute.
Mitchell
zK Ûtc ìxc 'ñ ´DICTIONARY TERMS:Prins washer A combination trough washer and jig in
[\B]Prins washer[\N]
An orthorhombic mineral, (Y,Ca,Fe,Th)(Ti,Nb)2 (O,OH)6 ; now
formally named aeschynite-(Y); forms series with aeschynite-(Ce) and with
tantalaeschynite-(Y); black; forms with other rare-earth minerals in
granite pegmatites and placers. Syn:blomstrandine
a. The volume of a length of embankment or excavation. Seelye, 1
b. The liquid mobile volume of a stream. Seelye, 1
c. An open crystal form with faces and their intersecting edges parallel
to the principal crystallographic axis. Prisms have three (trigonal), four
(tetragonal), six (ditrigonal or hexagonal), eight (ditetragonal), or
twelve (dihexagonal) faces. The nine-sided prisms of tourmaline are a
combination of trigonal and hexagonal prisms.
d. A long, narrow, wedge-shaped sedimentary body with width:thickness
between 5:1 and 50:1; e.g., a bajada adjacent to an escarpment. It is
typical of orogenic sediments formed during periods of intense crustal
deformation; e.g., the arkoses found in fault troughs. CF:tabular
Syn:wedge
a. Descriptive of a clast with length to width ratio between 1.5:1 and
3:1. CF:tabular
b. Pertaining to a sedimentary prism.
c. Pertaining to a crystallographic prism.
d. Descriptive of a crystal with one dimension markedly longer than the
other two.
e. Descriptive of two directions of cleavage.
f. Descriptive of a metamorphic texture in which a large proportion of
grains are prismatic and have approx. parallel orientation, giving a
lineated appearance in hand specimens and thin sections. CF:equant
See also:columnar
A small magnetic compass held in the hand when in use and equipped with
peep sights and a glass prism so arranged that the magnetic bearing or
azimuth of a line can be read (through the prism) from a circular
graduated scale at the same time that the line is sighted over.
AGI
Any crystallographic plane that is parallel to the principal axis of a
crystal.
Collectors' name for cordierite.
A telescope having an eyepiece fitted with a prism that reflects at 90
degrees . Hammond
Any solid, bounded by planes, whose end faces are parallel. Usually
understood to include also figures whose bounding surfaces are warped
surfaces. Seelye, 2
Adj. of prismoid; used in sedimentary petrology (not prismatic, which is a
crystallographic term).
A formula used in the calculation of earthwork quantities. It states that
the volume of any prismoid is equal to one-sixth its length multiplied by
the sum of the two end-areas plus four times the mid-area. CTD
A statistical measure (where zero is impossibility and one is certainty)
of the likelihood of occurrence of an event. AGI
a. Indicated reserves. See:reserves
b. A mineral deposit adjacent to developed ore but not yet proven by
development. CF:extension ore
A performance curve showing the expected results of a coal-preparation
treatment. BS, 5
Areas of coal or mineral believed to lie beyond the developed reserves but
not yet proven by development. See also:economic coal reserves
Syn:theoretical tonnage
a. A small tube containing a sensing element of electronic equipment,
which can be lowered into a borehole to obtain measurements and data.
Long
b. To conduct a search for mineral-bearing ground by drilling or boring.
Long
c. To lower drill rods, etc., to locate obstructions and/or to determine
the attitude of a piece of junk in a borehole. Long