See:trapezohedron
Having the symmetry or shape of a tetrahedron.
a. An isometric mineral, (Cu,Fe)12 Sb4 S13 , having
copper replaced by zinc, lead, mercury, cobalt, nickel, or silver; forms a
series with tennantite and freibergite; metallic; crystallizes in
tetrahedra; occurs in hydrothermal veins and contact metamorphic deposits;
a source of copper and other metals. Syn:gray copper ore; gray copper;
panabase; panabasite; stylotypite.
b. The mineral group freibergite, giraudite, goldfieldite, hakite,
tennantite, and tetrahedrite.
An isometric crystal form of four faces, each an equilateral triangle; the
alternate faces of an octahedron. Adj: tetrahedral.
An isometric crystal form (hk0) of 24 faces, each an isosceles triangle,
so arranged that four faces appear to replace each face of a cube
(hexahedron).
An atom, or group, having four valence bonds. Pryor, 3
a. Having a valence of 4. Webster 3rd
b. Having four valences; e.g., chlorine, which has valences of 1, 3, 5,
and 7. Webster 2nd; Handbook of Chemistry and Physics, 2
a. A hole; bore; a chimney, as for smoke. Webster 3rd
b. The tuyere of a furnace. Webster 2nd
The general physical appearance or character of a rock, including the
geometric aspects of, and the mutual relations among, its component
particles or crystals; e.g., the size, shape, and arrangement of the
constituent elements of a sedimentary rock, or the crystallinity,
granularity, and fabric of the constituent elements of an igneous rock.
The term is applied to the smaller (megascopic or microscopic) features as
seen on a smooth surface of a homogeneous rock or mineral aggregate. The
term structure is generally used for the larger features of a rock. The
two terms should not be used synonymously, although certain textural
features may parallel major structural features. Confusion may arise
because in some languages, e.g., French, the usage of texture and
structure are the reverse of the English usage. CF:structure
AGI
A monoclinic mineral, Y3 Si3 O10 (OH)(?) ; red to
pink; in pegmatites.
A metallic element resembling lead in physical properties; the metal is
silvery-white, but turns bluish-gray in air. Symbol, Tl. Occurs in
crooksite, lorandite, and hutchinsonite. It is also present in pyrites and
is recovered from the roasting of this ore in the manufacture of sulfuric
acid and from the smelting of lead and zinc ores. Used in low-melting
glasses, photocells, and infrared detectors.
Handbook of Chemistry and Physics, 3
a. The line of continuous maximum descent from any point on a land
surface; e.g., the line of greatest slope along a valley floor, or the
line crossing all contour lines at right angles, or the line connecting
the lowest points along the bed of a stream. Etymol: German Talweg, valley
way. Also spelled: talweg. AGI
b. In physical geography, a term adopted into English usage signifying the
line of greatest slope along the bottom of a valley; i.e., a line drawn
through the lowest points of a valley in its downward slope. It thus marks
the natural direction of a watercourse. AGI
c. In hydraulics, the line joining the deepest points of a stream channel.
AGI
d. By many geomorphologists, the term is used as a syn. for valley
profile. AGI
e. The center line of the principal navigational channel of a waterway
constituting a boundary between political subdivisions. Hunt
a. A mixture of kainite and halite. English
b. Carbon oxysulfide, COS, as a natural gas.
A hexagonal mineral, Ca6 Si2 (CO3 )2 (SO (sub
4) )2 (OH)12 .24H2 O ; white; fibrous.
A small building, designed for thawing dynamite, of such size as to
provide enough thawed dynamite for a day's work. Fay
a. A method of working permanently frozen ground in which water at a
temperature of from 50 to 60 degrees F (10 to 15.6 degrees C) is pumped
through pipes down into the frozen gravel. The pipes through which the
water is pumped are called sweaters. See also:steam thawing; thaw pipe.
Lewis
b. In dynamiting, warming to reduce risk of premature explosion that might
originate from rupture of frozen crystal. Performed in thaw house or
thawing kettle using steam or hot water. With modern methods of explosive
manufacture, the need has practically disappeared. Pryor, 3
A double kettle, built somewhat like a farina boiler, having two
compartments, an outer compartment, which is filled with hot water and
which entirely surrounds the inner compartment that contains the dynamite
to be thawed. It is provided with a lid for retaining the heat.
Fay
A string of pipe lowered into a string of drill rods that is frozen in a
borehole drilled into permafrost, through which water is circulated to
thaw the ice and free the drill rods. See also:thawing
In the coke products industry, one who thaws frozen materials in railroad
cars by heating sections of shed where cars are spotted. DOT
See:translucent humic degradation matter
A carbonaceous constituent of torbanite, occurring in the form of a
solidified clear, jellylike substance, something like solidified
dopplerite, but probably of unlike chemical composition. Tomkeieff