A general term for lava that exhibits pillow structure, mostly basalts and
andesites that erupted and flowed under water. The ocean floor sodium-rich
basalts known as spilites are commonly pillowed.
A structure, observed in certain extrusive igneous rocks, that is
characterized by discontinuous pillow-shaped masses ranging in size from a
few centimeters to a meter or more in greatest dimension (commonly between
30 cm and 60 cm). The pillows are close-fitting, the concavities of one
matching the convexities of another. The spaces between the pillows are
few and are filled either with material of the same composition as the
pillows, with clastic sediments, or with scoriaceous material. Grain sizes
within the pillows tend to decrease toward the exterior. Pillow structures
are considered to be the result of subaqueous extrusion, as evidenced by
their association with sedimentary deposits, usually of deep-sea origin.
See also:pillow lava; mammillary structure. AGI
a. A cylindrical steel bar extending through and about 8 in (20 cm) beyond
the face of a reaming bit. It acts as a guide that follows the original
unreamed part of the borehole and hence forces the reaming bit to follow
and be concentric with the smaller-diameter, unreamed portion of the
original borehole. Syn:reaming pilot
Long b. A cylindrical diamond-set plug, of somewhat smaller diameter than the
bit proper, set in the center and projecting beyond the main face of a
noncoring bit. See also:pilot bit; stinger. Long
Said of the texture of the groundmass of a holocrystalline igneous rock in
which lath-shaped microlites (typically plagioclase) are arranged in a
glass-free mesostasis and are generally interwoven in irregular unoriented
fashion. CF:trachytic
A noncoring bit with a cylindrical diamond-set plug of somewhat smaller
diameter than the bit proper set in the center and projecting beyond the
main face of the bit. See also:plug bit; drag bit. Long
The weight attached to a shaft plumbline for the purpose of lowering the
line down the shaft. BS, 7
A small burner kept lighted to rekindle the principal burner when desired
(as in a flash boiler). The light so maintained is called a pilot light or
pilot flame. Webster 3rd; Fay
A small drill used to start a hole in order to insure a larger drill
running true to center. Crispin
a. A small hole drilled ahead of a full-sized, or larger borehole.
Long
b. A borehole drilled in advance of mine workings to locate water-bearing
fissures or formations. Long
c. A small tunnel driven ahead of, and subsequently enlarged to the
diameter required in the following full-size tunnel. Long
See:cover
A small electric bulb that lights when power is turned on in a circuit.
Hammond
The method of excavating a tunnel by driving a small tunnel ahead, and
then enlarging its dimensions.
A small-scale processing plant in which representative tonnages of ore can
be tested under conditions which foreshadow (or imitate) those of the
full-scale operation proposed for a given ore. Pryor, 4
An assemblage of a pilot, a pilot reaming bit, and a reaming barrel.
See also:pilot; pilot reaming bit. Long
A box-threaded, diamond-set, annular-shaped bit designed to be coupled to
a pilot and used to ream a borehole to a specific casing size.
See also:pilot
The taking of preliminary samples of a mineral deposit to study its mode
of occurrence and its detailed structure. Syn:reconnaissance sampling
Nelson
Sequence control by means of a pilot cable is effected by means of a
low-voltage supply from one contactor panel to the next, or by means of a
line voltage pilot cable. Each contactor has an auxiliary contact that
controls the supply to the next contactor. In the low-voltage system, the
secondary of each potential transformer is earthed at the preceding panel
through an auxiliary switch which closes with the contactor. Until these
secondary potential transformer circuits are completed, by closing the
auxiliary contact, the next conveyor cannot start.
See also:sequence starting
See:pilot tunnel
A small tunnel or shaft excavated in the center, and in advance of the
main drivage, to gain information about the ground and create a free face,
thus simplifying the blasting operations. Nelson
a. A small balanced valve, operated by a governor or by hand, which
controls a supply of oil under pressure to the piston of a servometer or
relay connected to a large control valve, which it is desired to operate.
Also called relay valve. CTD
b. In a compressor, an automatic valve that regulates air pressure.
Nichols, 1
A half-cylinder member, about 5 in (12.7 cm) long, coupled to the lower
end of a Hall-Rowe deflection wedge, by means of which the deflection
wedge may be oriented in a specific manner in reference to a matching
half-cylinder surface on the upper end of the wedge (drive wedge). This is
driven into the wooden plug placed about 8 ft (2.4 m) below the point in a
borehole where a deflection is to be made. Also called wedge pilot.
Long