See:peridot
A general term for a coarse-grained plutonic rock composed chiefly of
olivine with or without other mafic minerals such as pyroxenes,
amphiboles, or micas, and containing little or no feldspar. Accessory
minerals of the spinel group are commonly present. Peridotite is commonly
altered to serpentinite. AGI
See:Ceylonese peridot; peridot.
A method of blasting in tunnels, drifts, and raises, designed to minimize
overbreak and leave clean-cut solid walls. Holes in the outside row are
loaded with very light, continuous explosive charges and are fired
simultaneously, so that they shear from one hole to the other.
Nelson
In mine ventilation, the linear distance in feet of the airway perimeter
rubbing surface at right angles to the direction of the airstream.
A crystal of one species enclosing one of another species.
Webster 3rd
a. The geochronologic unit lower in rank than era and higher than epoch,
during which the rocks of the corresponding system were formed. It is the
fundamental unit of the worldwide geologic time scale. AGI
b. A term used informally to designate a length of geologic time; e.g.,
glacial period. AGI
c. The interval of time required for the completion of a cyclic motion or
recurring event, such as the time between two consecutive like phases of
the tide or a current. AGI
d. The duration of one complete cycle of a periodic function; the
reciprocal of the frequency of such a function. The independent variable
is limited to time. ASM, 1
e. The elements between an alkali metal and the rare gas of next highest
atomic number, inclusive, occupying one (a short period) horizontal row or
two (a long period) horizontal rows in the periodic table. CTD
f. The time required for the power level of a reactor to change by the
factor 2.718, which is known as e. Lyman
The physical and chemical properties of the elements depend on the
structure of their atoms and are for the most part periodic functions of
the atomic number. See also:periodic table
Pertains to periodic change in the direction of flow of the current in
electrolysis. It applies to the process and also to the machine that
controls the time for both directions. Symbol, PR. ASM, 1
An arrangement of elements based on the periodic law and proposed in
various forms that are usually either short with only short periods (as in
Mendeleev's original table) or long with long as well as short periods (as
in most modern tables). See also:periodic law
A fault along the perimeter of a geologically elevated or depressed
region. AGI
The distance a given point on the perimeter of a rotating circular object
travels, expressed in feet or meters per second; sometimes incorrectly
called lineal travel by some drillers. Syn:surface speed
This pump--sometimes called a regenerative pump--is classified with
centrifugal pumps, but is designed to develop several times the head
obtained from a centrifugal pump having the same-diameter impeller and the
same speed. The maximum head developed does not have the same relation to
the impeller diameter and speed of the centrifugal pump; it involves size
and spacing of the impeller vanes, fluid channels, and other factors.
Pit and Quarry
A mine ventilation system in which the upcast shaft for taking air out of
a mine is situated at the limits of the mining field or away from the
downcast shaft. Also called transverse or one-way ventilation.
Syn:transverse ventilation
Said of an isothermal reversible reaction in a crystallizing melt or magma
in which a liquid phase reacts with a solid phase to produce another solid
phase on cooling. ASM, 1
a. A siliceous volcanic glass having numerous concentric spherical cracks
that give rise to an onion-skin structure. Most perlite has a higher water
content than obsidian. When perlite is heated to the softening point, it
expands, or pops to form a light fluffy material similar to pumice. It is
used as lightweight aggregate in concrete, as insulation for liquid fuels,
and in potting soils.
b. A pearly volcanic glass.
a. Said of the texture of a glassy igneous rock that has cracked owing to
contraction during cooling, the cracks forming small spheruloids. It is
generally confined to natural glass, but occasionally found in quartz and
other noncleavable minerals and as a relict structure in devitrified
rocks. AGI
b. Pertaining to or characteristic of perlite. AGI
A permanently frozen layer of soil or subsoil, or even bedrock, which
occurs to variable depths below the Earth's surface in arctic or subarctic
regions. It underlies about one-fifth of the world's land area.
a. Boreholes drilled in subsoil and rocks in which the contained water is
permanently frozen. Long
b. Holes drilled into perenially frozen ground that may be superficial
unconsolidated material, bedrock, and ice. When no ice is present, it is
called dry permafrost.
An iron-nickel alloy with high magnetic permeability. Nelson
The adjustment of a surveying instrument that is made infrequently and not
at each setup. See also:temporary adjustment