Measures the intensity of the light scattered at an angle from the
incident beam by a dust cloud, and correlates well with the concentration
determined by the thermal precipitator or the surface area calculated from
such a count. However, it needs to be calibrated for each type of dust
cloud, owing to difference in mineralogical content, against the thermal
precipitator. Sinclair, 1
Logwood digested in an aqueous solution of aluminum chloride; used to
distinguish calcite and dolomite. Calcite and aragonite are stained violet
after treatment for about 10 min, but dolomite remains unchanged.
A contracted form of the names leucite and nephelite; suggested as an
alternative group name for the feldspathoid minerals. CF:feldspathoid
A triclinic mineral, Pb6 (Ag,Cu)2 As4 S13 .
A screwed extension rod for prolonging a well-boring auger or bit.
Standard, 2
The distance measured along a straight line parallel to the rope in which
the strand forms one complete spiral around the rope or the wires around
the strand. See also:lay
a. The depth of the hole in which the powder is placed, or the size of the
block of coal to be loosened by a single blast measured parallel with the
hole.
b. In open pit mining, the distance from the first drill hole to the last
drill hole along the bank.
Eng. In tunnel construction, the successive sections in which a tunnel is
executed. Shaft lengths are directly under the working shaft; side lengths
are on each side of the shaft length; leading lengths are prolongations of
the tunnel from the side lengths; and junction lengths complete the
portion of the tunnel extending between two shafts, or between a shaft and
an entrance.
a. A green variety of orthoclase at Lenni Mills, Delaware County, PA.
Syn:delawarite
b. A variety of vermiculite.
a. A geologic deposit bounded by converging surfaces (at least one of
which is curved), thick in the middle and thinning out toward the edges,
resembling a convex lens. A lens may be double-convex or plano-convex.
See also:lentil; lenticular. ---v. To disappear laterally in all
directions; e.g., a unit is said to lens out within a mapped area.
AGI
b. In optics, a device that modulates the direction taken by a transient
beam of light. Pryor, 3
Pyrite, round or oval in plan and lenticular in section, ranging up to 2
to 3 ft (0.6 to 0.9 m) in thickness and several hundred feet in the
greatest lateral dimension, that is found in coalbeds. Sometimes called
kidney sulfur. Mitchell
The process of grinding pieces of flat sheet glass (or pressed blanks) to
the correct form of the lens. Cast-iron tools of the correct curvature,
supplied with a slurry of abrasive and water, are used. CTD
The thinning-out of a stratum in one or more directions.
a. A large or small lens-shaped stratum or body of rock; a lentil.
AGI
b. A lens-shaped rock fragment of any size. AGI
a. Resembling in shape the cross section of a lens, esp. of a
double-convex lens. The term may be applied, e.g., to a body of rock, a
sedimentary structure, or a mineral habit. AGI
b. Pertaining to a stratigraphic lens or lentil. Syn:lentiform
AGI
Impure concretionary hematite.
A small lentil. AGI
See:lenticular
a. A minor rock-stratigraphic unit of limited geographic extent, being a
subdivision of a formation and similar in rank to a member, and thinning
out in all directions; a geographically restricted member that terminates
on all sides within a formation. CF:tongue
b. A lens-shaped body of rock, enclosed by strata of different material; a
geologic lens. See also:lenticule; lenticle. AGI