Any level surface, such as mean sea level, used as a reference from which
elevations are reckoned; a datum plane. AGI
a. A horizontal plane used as a reference from which to reckon heights or
depths. Hunt
b. A permanently established horizontal plane, surface, or level to which
soundings, ground elevations, water-surface elevations, and tidal data are
referred; e.g., mean sea level is a common datum plane used in topographic
mapping. Syn:datum level; reference level; reference plane.
See also:datum
a. The level at which water is first struck in a shaft sunk on a reef or
gutter. Zern
b. Ground or surface water level used as a reference for all other
measurements.
See:zippeite
a. Scot. The floor of a coal seam or where holing is done. Nelson
b. Underclay; soft fireclay. Arkell
The element formed when a radioactive element undergoes radioactive decay.
The latter is called the parent. The daughter may or may not be
radioactive. CCD, 2
Rock crystal variety of quartz.
The law governing a twinning observed in the hexagonal system commonly
shown by quartz in which two righthand or two lefthand crystals
interpenetrate after one has revolved 180 degrees about the twinning axis.
Hess
Transformation twinning about the [0001] direction with an irregular
contact surface in quartz. Syn:electrical twinning
A method of geometrically determining the detonation velocity of an
explosive material by using a lead witness plate and detonating cord
ignited by the test explosive. Meyer
A trigonal mineral, (La,Ce)(Y,U,Fe)(Ti,Fe)20 (O,OH)38 ;
crichtonite group; radioactive; metamict; in high-temperature hydrothermal
veins, pegmatites, and mafic igneous rocks; occurs in all stages of
intergrowth and exsolution with ilmenite and hematite, and is an ore of
uranium. Syn:ferutile
A greenish-yellow variety of beryl.
See:Davis cutter bit
A rotary drill similar to the diamond core drill except that the annular
groove is cut either by a steel chisel or by a plain hollow rod using
chilled shot. When the core is of sufficient length to be withdrawn, some
grit is added to the mud flush, which becomes wedged tightly between the
core and base of the barrel. When the rods are raised the core is broken
off and brought to the surface. Nelson
An annular-shaped, sawtoothlike bit used on shot drills to cut core in
soft formations in which shot is ineffective as a cutting medium.
Syn:Davis bit
A long, one-hearth reverberatory furnace, heated by lateral fireplaces for
roasting sulfide ore. Fay
An instrument for testing the magnetic content of ores and for checking
the efficiency of wet magnetic separators recovering magnetite and
ferrosilicon in heavy-media processes. Nelson
A mixture of crandallite and an apatite. Syn:dennisonite
A railway tire consisting of a soft plate and boss, and a wear- resistant
tread of water-toughened manganese steel, cast integrally within.
Osborne
A monoclinic mineral, MnAl6 Si4 O17 (OH)2 .