a. The distance along a crystallographic axis to its intersection with a
crystal face. This intercept is a rational number because the axial unit
length of each mineral is selected to make it so. The ratio of these
intersections of a face with each of the crystallographic axes constitutes
a parameter, such as Miller indices, that defines the crystal face.
CF:indices of a crystal face; crystallographic axis; Miller indices.
b. The part of the rod seen between the upper and lower stadia hairs of a
transit or telescopic alidade; e.g., a stadia interval.
A channel excavated at the top of earth cuts, or at the foot of slopes, or
at other critical places to intercept surface flow; a catch drain.
Seelye, 1
A drain that intercepts and diverts water before it reaches the area to be
protected. Also called curtain drain. Nichols, 1
a. That portion included between two points in a borehole, as between the
point where the hole first encounters a specific rock or mineral body and
where the hole enters a different or underlying rock formation.
Long
b. In crystallography, the distances cut off on axes of reference by
planes. Fay
See:delay time
a. A radiator in which air is cooled while moving from low-pressure to
high-pressure cylinders of a two-stage compressor.
See also:two-stage compression
b. In multistage compression of air, a cooling arrangement between stages.
See also:aftercooler
c. A cooling device used on a turbocharged diesel engine to reduce the air
volume between the turbocharger and the cylinders.
Extraction of heat from a compressed gas between two stages of compression
in order to improve the efficiency of compression. Strock, 2
The internal or dihedral angle between two faces of a crystal. It is also
the "angle of dip" between faces.
Tension at interfaces between the various phases of a system; may include
solid, liquid, and gas interfaces, varying in their combinations and
qualities. Pryor, 3
The contractile force of an interface between two phases. ASM, 1
The meeting of two wave systems resulting in increased amplitude
(constructive interference) if they are in phase, i.e., crest to crest,
and decreased amplitude (destructive interference) if they are out of
phase, i.e., crest to trough. In polarized-light microscopy (PLM), phase
differences are generated when white light passes through an anisotropic
(i.e., doubly refracting) crystal or crystal fragment, these differences
being determined primarily by birefringence, light wavelength, and crystal
thickness. Waves of light in different parts of the visible spectrum
interfere both constructively and destructively when resolved in the
microscope analyzer to give an interference color. Since anisotropic
minerals have a range of birefringence, interference colors are useful as
an aid to their identification. See also:optic sign;
index of refraction.
One of the spectral colors produced by the strengthening or the weakening
of certain wavelengths of a composite beam of light in consequence of
interference. This is an important characteristic in determining minerals
in thin section or in fragments under the polarizing microscope.
Webster 3rd
a. An optical figure composed of a series of spectrally colored rings
combined with a blank cross (if uniaxial) or a series of spectrally
colored curves or rings with two black parabolic curves called isogyres
(if biaxial). The figure is observed when a properly oriented thin section
or fragment of a mineral is examined in convergent light through the
polarizing microscope. The interference figure, which is caused by the
birefringence of the mineral and by the orientation of the mineral so that
it presents an optic axis in the field of the microscope, is one of the
most valuable optical aids in identifying minerals. Also called the
direction image.
b. An optical pattern produced by conoscopic illumination of anisotropic
crystals which appears on a spherical focal surface located above the
objective lens of a polarized-light microscope. CF:melatope
A combustible-gas detector based on the velocity of light. A beam of light
is split into two parts that pass respectively through chambers containing
pure air and the test air at velocities characteristic of the gases. When
methane is present, the light beams are out of step and this movement
becomes a measure of the methane concentration. See also:refractometer
Nelson
The area between two rivers flowing in the same general direction.
Syn:interstream area
Between formations, such as an interformational unconformity.
CF:intraformational
Corrosion that occurs preferentially at grain boundaries of a metal or
alloy.
a. Of coal and mineral matter, naturally associated and separable only by
crushing or grinding. BS, 5
b. In crystallography, a descriptive term for mineral species that have
crystallized simultaneously and therefore become intertwined or
interlocked. Pryor, 3
The state of interlocking of grains of two different minerals as a result
of their simultaneous crystallization. CF:graphic granite
Horizontal angle between adjacent sides of a polygon, measured within the
polygon. Seelye, 2
U.S. Includes Eastern Interior Field, Illinois, Indiana, and Kentucky;
Western Interior Field, Great Plains States from Iowa to Arkansas;
Southwestern Field, Texas; and Northern Field, Michigan.
Bateman, 1