A type of jib crane carried on a four-legged portal frame, which runs
along rails. See also:goliath crane; platform gantry. Hammond
A term encountered in disputes over what constitutes compensable "working
time" under Federal laws. Portal literally means "entrance" and, in
underground coal mining, portal refers to the mine mouth or entry at the
surface. Hence, portal-to-portal as a descriptive term means strictly
elapsed time from entry through the portal to exit on return. BCI
Port roof of a tank.
See:scraper plow
A long iron bar attached to a forging, or a piece in process of forging,
by which to swing and turn it. Standard, 2
The opening or passageway connecting the inside of a bit or core barrel to
the outside and through which the circulating medium is discharged.
Long
A calcium-aluminum silicate produced by fusing or clinkering limestone and
clay in a kiln so as to drive off carbon dioxide and produce an oxide
glass. The clinker is ground very fine and, when mixed with water, will
recrystallize and set. It is combined with aggregate to form concrete. The
name is from a resemblance to the Portland limestone of England.
A mixture of portland cement, sand, and water. See also:cement mortar
Nelson
A hexagonal mineral, Ca(OH)2 ; occurs in skarns; an important
constituent of portland cement.
A series of limestone strata, belonging to the Oolite group (Upper
Jurassic) on the Isle of Portland, Dorsetshire, England. Most of the
building stone used in London is from these quarries.
a. A yellowish-white, oolitic limestone from the Isle of Portland (a
peninsula in southern England), widely used for building purposes.
AGI
b. A purplish-brown sandstone (brownstone) from Portland, CT. AGI
A flat diamond, sometimes with several rows of facets around its edge;
used for covering very small portraits. Standard, 2
An oxygenated hydrocarbon from the Great Western mercury mine, Lake
County, CA. It occurs in plates and nodules, sometimes brittle,
occasionally hard; the color is light green to reddish-brown; and sp gr,
0.85 to 0.985. Fay
Mining claim that is in a position to contain a lode if it continues in
the direction in which it has been proved in other claims, but which
itself has not been proved.
a. Electrically, a point at a relatively high potential with respect to
another point. A positive ion is one in which a particle, molecular or
atomic, has ceased to be neutral owing to loss of one or more electrons.
Pryor, 3
b. Positive ore is ore that has been proved to exist by being blocked out
in panels sampled at close intervals on all four sides so as to establish
its quality and quantity beyond reasonable doubt.
The upper confining bed of an aquifer whose head is above the upper
surface of the zone of saturation; i.e., above the water table. Little
used. AGI
An optically positive crystal. AGI
A device installed in or on a mine track to derail runaway cars or trips.
This device is held open by a spring, necessitating that a worker hold it
closed while a trip passes over it. Hess
positive-discharge bucket elevator
A spaced bucket-type elevator in which the buckets are maintained over the
discharge chute for a sufficient time to permit free gravity discharge of
bulk materials. See also:bucket elevator
A pump which discharges the same amount of water for a given power,
regardless of the head against which it operates.
See also:bladder pump