A deposit of sand or gravel that contains particles of gold, ilmenite,
gemstones, or other heavy minerals of value. The common types are stream
gravels and beach sands. See also:alluvial deposit; beach placer.
a. A mining claim located upon gravel or ground whose mineral contents are
extracted by the use of water, by sluicing, hydraulicking, etc. The unit
claim is 1,320 ft2 (122.6 m2 ) and contains 10 acres
(4.1 ha). See also:mining claim
b. Ground with defined boundaries that contains mineral in the earth,
sand, or gravel; ground that includes valuable deposits not fixed in the
rock. See also:claim; lode claim.
c. The maximum size of a placer claim is 20 acres (8.1 ha). Association
claims of two or more persons may be located up to an area of 160 acres
(64.8 ha) for eight persons. Placer claims must have a discovery. They
should be staked, a location notice posted, and recorded in the same
manner as for lode claims, stating the mineral for which the location in
made. Lewis
a. The action of mining by placer methods. Craigie
b. A place at which placer mining is or may be carried on. Craigie
Gold occurring in more or less coarse grains or flakes and obtainable by
washing the sand, gravel, etc., in which it is found. Also called alluvial
gold. See also:stream gold
Ground where placer mining can be done; i.e., where valuable minerals can
be obtained by digging up the earth and washing it for the valued mineral.
Craigie
A location of a tract of land for mineral-bearing or other valuable
deposits upon or within it that are not found within lodes or veins in
rock in place; a claim of a tract of land for the sake of the loose
deposits on or near its surface. Ricketts
a. A deposit of sand, gravel, or talus from which some valuable mineral is
extracted. Hess
b. See:placer mining
a. The extraction of heavy mineral from a placer deposit by concentration
in running water. It includes ground sluicing, panning, shoveling gravel
into a sluice, scraping by power scraper and excavation by dragline,
dredge or other mechanized equipment. Nelson
b. Extracting the gold or other mineral from placers, wherever
situated--in dry channels and in channels temporarily filled with water.
The mineral may be found in deep channels, in navigable streams, or in
estuaries or creeks and rivers where the sea ebbs and flows.
Ricketts
c. That form of mining in which the surficial detritus is washed for gold
or other valuable minerals. When water under pressure is employed to break
down the gravel, the term hydraulic mining is generally employed. There
are deposits of detrital material containing gold which lie too deep to be
profitably extracted by surface mining, and which must be worked by
drifting beneath the overlying barren material. The term "drift mining" is
applied to the operations necessary to extract such auriferous material.
See also:dredge
d. The extraction and concentration of heavy metals or minerals from
placer deposits by various methods, generally using running water.
CF:alluvial mining; hydraulic mining; drift mining. AGI
See:maucherite
A fossil resin found in Switzerland. Tomkeieff
See:plagiohedral
a. Any of a group of feldspars containing a mixture of sodium and calcium
feldspars, distinguished by their extinction angles; crystal; triclinic;
Mohs hardness, 6; and sp gr, 2.6 to 2.7. Bennett
b. A series of triclinic feldspars of general formula: (Na,Ca)Al(Si,Al)Si
2 O6 ; at high temperatures it forms a complete crystal
solution series from albite, NaAlSi3 O8 , to anorthite, An,
CaAl2 Si2 O8 ; the series is arbitrarily subdivided
and named according to increasing mole fraction of the An component:
albite (An 0% to 10%), oligoclase (An 10% to 30%), andesine (An 30% to
50%), labradorite (An 50% to 70%), bytownite (An 70% to 90%), and
anorthite (An 90% to 100%). The Al:Si ratio ranges with increasing An
content from 1:3 to 1:1. Plagioclase feldspars are common rock-forming
minerals, have characteristic polysynthetic twinning, and commonly display
zoning. The term was originally applied to all feldspars having an oblique
angle between the two main cleavages. CF:alkali feldspar; orthoclase.
Syn:sodium-calcium feldspar
A porphyritic extrusive rock with phenocrysts of plagioclase and quartz in
a groundmass of orthoclase and quartz. Also called plagioliparite.
Syn:dellenite
Having the cleavage of plagioclase; breaking obliquely.
Standard, 2
Having an oblique spiral arrangement of faces; specif., being a group of
the isometric system characterized by 13 axes of symmetry but no center or
planes. Also spelled plagihedral. Webster 3rd
A monoclinic mineral, Pb5 Sb8 S17 ; metallic black to
lead-gray; forms stubby tablets; an uncommon associate of other lead
sulfosalts in hydrothermal veins.
a. An extent of level, or nearly level, land; a region not noticeably
diversified with mountains, hills, or valleys. Fay
b. A flat, gently sloping or nearly level region of the sea floor.
Hunt
c. Archaic. Relatively free of gaseous inclusions. ASTM
A clinometer having only its upper end threaded to fit drill rods. Also
called end clinometer. See also:clinometer
wedge clinometer. Long
Concrete with no reinforcement. Hammond
A detonator for use with a safety fuse. It consists of an aluminum tube
closed at one end and partly filled with a sensitive initiating explosive.
The tube is only partially filled because a plain detonator is always used
in conjunction with a safety fuse, and the empty space enables the fuse to
be inserted into the tube until it comes into contact with the detonating
composition. The safety fuse is then secured in position by indenting the
detonator tube, this process being known as crimping. The combination of
safety fuse and plain detonator is called a capped fuse.
BS, 12; McAdam, 2
A pilot in the surface of which no cutting points, such as diamonds or
slugs, are inset. See also:pilot