A triclinic mineral, (Na,Ca)[(Si,Al)AlSi2 O8 ] , NaSi 50 to
70 mol %, CaAl 50 to 30 mol %; of the plagioclase series of the feldspar
group with prismatic cleavage; white to gray; a common rock-forming
mineral in andesites, differentiated gabbros, some anorthosites, and as
detrital grains.
A coarse-grained igneous rock almost entirely composed of andesine. It was
named by Turner in 1900. CF:anorthosite
AGI
A dark-colored, fine-grained extrusive rock that, when porphyritic,
contains phenocrysts composed primarily of zoned sodic plagioclase (esp.
andesine) and one or more of the mafic minerals (e.g., biotite,
hornblende, pyroxene), with a groundmass composed generally of the same
minerals as the phenocrysts, although the plagioclase may be more sodic,
and quartz is generally present; the extrusive equivalent of diorite.
Andesite grades into latite with increasing alkali feldspar content, and
into dacite with more alkali feldspar and quartz. It was named by Buch in
1826 from the Andes Mountains, South America. AGI
An orthorhombic mineral, PbAgSb3 S6 . Syn:sundtite
An isometric mineral, 8[Ca3 Fe2 Si3 O12 ] ;
never pure; garnet group; in yellow, green, red, brown, or black
dodecahedral and trapezohedral crystals, or may be massive; in calcareous
metasediments and placers. Varieties include topazolite, demantoid,
melanite, aplome, and bredbergite.
A direction of coal face roughly halfway between the main (bord) and
secondary (end) cleavages; on the cross. Mason
An instrument used in the determination of the particle size of clays by
the sedimentation method. Dodd
A device for particle size analysis. It consists of (1) a feed vessel or
tube, (2) a large hydraulic classifier, (3) an intermediate classifier,
and (4) a graduated measuring vessel. Dodd
An orthorhombic mineral, (Cu,Fe)Fe3 (PO4 )3 (OH) (sub
2) ; in bluish-green globules with radial structure.
Broken off by wind erosion and rounded by wind action.
A continuous record of wind speed and direction given by an anemograph.
Hammond
A self-recording anemometer giving a continuous trace of the direction and
velocity of surface wind. In the Dines tube anemograph, the wind pressure
acts upon the opening of a tube arranged as a vane to face in the
direction of the wind. Pressure is transmitted through the tube to a float
carrying a pen, the height of which indicates the wind velocity.
Hammond
a. An upturned form of calcite stalactite; its form is supposed to have
been caused by air currents. English
b. A stalactite with one or more changes in its growth axis.
Syn:helictite
An instrument for measuring air velocity. It consists of a small fan from
3 to 6 in (7.6 to 15.2 cm) in diameter that is rotated by the air current.
By simple gearing, the number of revolutions of the fan is recorded on
dials. It is held in the mine airway for the exact number of minutes (N),
the instrument being moved steadily over the entire area. The difference
between the initial and the final readings on the dials, divided by N,
gives the velocity of the air in feet per minute. Instruments are
available for velocities from near zero to 6,000 ft/min (1.83 km/min),
also with extension and remote control handles.
See also:vane anemometer; self-timing anemometer. Nelson
Consists essentially of an aneroid barometer and a revolving drum. The
movement of the evacuated spring can is transmitted and magnified through
a system of levers so that it is finally traced by means of a stylo on the
graph paper attached to the revolving drum. The drum is rotated by
clockwork, and can be of either the 24-h or the 7-day type. The graph
paper is usually marked off in hourly intervals, so that a complete record
of the atmospheric pressure at any instant may be obtained. These
barographs are used extensively in mining and in meteorological offices.
Morris
An instrument for measuring atmospheric pressure, built first by Lucien
Vidie in about 1843. Basically, variation in pressure with changes in
altitude is determined by the movements of the elastic top of a metallic
box from which the air has been partly exhausted. Used generally in
measuring altitude. AGI
a. An explosive material consisting of ammonium nitrate and fuel oil.
b. A blasting product, with approx. 94.5% industrial-grade ammonium
nitrate and 5.5% No. 2 grade diesel fuel oil for a nearly oxygen-balanced
mix; available in bulk form for onsite mixing of the AN and fuel or in
50-lb (23-kg) premixed bags as pourable forms. A heavy ANFO product is
comprised of up to 45% to 50% ammonium nitrate emulsion mixed with prilled
ANFO to increase the bulk density of ANFO; it has improved strength and
provides good water resistance in comparison to ANFO. SME, 1
A triclinic mineral, Fe4 (AsO4 )2 O3 ;
brownish-black, encrusted on andesite in northwestern Argentina.
A two-limbed beam used for turning angles in shafts, etc. Zern
A brace used to prevent mine timbers from riding or leaning; a brace
across an interior angle. Fay
Drill holes converge, so that a core is blasted out. This leaves an open
or relieved cavity or free face for the following shots, which are timed
to ensue with a fractional delay. Pryor, 3