In seismic operations, a dip determined by spreads placed in four
directions from a shot point. Three are essential, and the fourth serves
as a check. AGI
A variety of rhodonite containing up to 10% zinc.
See:iron pan
A nepheline syenite with predominant orthoclase and a trachytic texture.
Not a name in the I.U.G.S. classification of plutonic rocks.
Syn:midalkalite
A portion of an unconsolidated sediment or of a crushed consolidated rock
sample or of a crushed ore or mineral sample that has been separated by
some method, and is distinguished in some manner from all the other
portions (or fractions) comprising the whole sample being analyzed. Also a
fraction may be separated and defined on the basis of its mineral content,
its specific gravity or density, its magnetism or lack of magnetism, or
its solubility or insolubility in acid.
a. Crystallization in which the early-formed crystals are prevented from
equilibrating with the liquid from which they grew, resulting in a series
of residual liquids of more extreme compositions than would have resulted
from equilibrium crystallization. CF:crystallization differentiation
Syn:fractionation
b. Controlled precipitation from a saline solution of salts of different
solubilities, as affected by varying temperatures or by the presence of
other salts in solution. AGI
A distillation process for the separation of the various components of
liquid mixtures. An effective separation can only be achieved by the use
of fractionating columns attached to the still. CTD
A method of sampling sometimes used at points where coal or mineral is
loaded or unloaded by shoveling. Every tenth (or other number) shovelful
is deposited separately as sampling material. Nelson
An apparatus for separating the high-boiling and low-boiling fractions of
a substance, whereby the fractions with the lowest boiling point distill
over. The efficiency depends on the column length and on the number of
bubble plates used.
a. The separation of (1) a substance from a mixture, such as the
separation of one isotope from another of the same element; (2) one
mineral or group of minerals from a mixture; or (3) one size fraction from
a mixture. AGI
b. Separation of chemical elements in nature, by processes such as
preferential concentration of an element in a mineral during magmatic
crystallization, or differential solubility during rock weathering.
See:fractional crystallization
The study of the surfaces of fractures, esp. microscopic study.
AGI
a. A general term for any break in a rock, whether or not it causes
displacement, due to mechanical failure by stress. Fracture includes
cracks, joints, and faults. AGI
b. The breaking of a mineral other than along planes of cleavage or
parting. A mineral can be described in part by its characteristic
fracture; e.g., uneven, fibrous, conchoidal, or hackly. CF:parting;
uneven fracture. AGI
c. Deformation due to a momentary loss of cohesion or loss of resistance
to differential stress and a release of stored elastic energy. CF:flow
Syn:rupture
A type of cleavage that occurs in deformed but only slightly metamorphosed
rocks and that is based on closely spaced, parallel joints and fractures.
CF:flow cleavage
See:fractured ground
Rock formation shattered and crisscrossed with fissures and fractures.
CF:broken ground
The fracture dome is the zone of loose or semiloose rock which exists in
the immediate hanging or footwall of a stope. In some mines it may extend
into the walls for a considerable distance. In a rock burst it becomes
greatly extended. Spalding
Porosity resulting from the presence of openings produced by the breaking
or shattering of an otherwise less pervious rock.
The differential stress at the moment of fracture. Syn:breaking stress
A set or group of contemporaneous fractures related by stress. AGI
a. A rock or mineral particle larger than a grain. AGI
b. A piece of rock that has been detached or broken from a preexisting
mass; e.g., a clast produced by volcanic, dynamic, or weathering
processes. AGI
Formed from fragments of preexisting rocks. See also:clastic