A coal cutter in which the horizontal jib can be adjusted vertically to
cut at different levels in the seam, for example, an overcut. The center
of gravity of such a machine makes it top heavy and less stable than the
ordinary undercutter. See also:overcutting machine;
universal coal cutter. Nelson
A vertical rotating jib fitted with cutter picks and driven from the end
sprocket of the bottom jib of a coal cutter. The turret jib is
satisfactory in seams where the coal parts readily from the roof and is
not too hard. See also:mushroom jib; curved jib. Nelson
A name for chlorastrolite (pumpellyite), esp. the green variety with
patches of color; also, turquoise matrix or variscite matrix.
See:septarium
Large, nodular concretions found in certain clays and marls. In form, they
have a rough resemblance to turtles, and this appearance is increased by
their being divided into angular compartments by cracks filled with spar,
reminding one of the plates on the shell of a turtle. Fay
An important source of raw material for silica refractories. A typical
analysis is 97.8% SiO2 , 0.9% Al2 O3 , 0.7% Fe (sub
2) O3 , and 0.4% alkalies. Dodd
A former name for calciocopiapite.
a. A white alloy, resembling German silver, used in making tableware,
etc., with varying proportions of copper, zinc, nickel, and sometimes a
little lead or iron. Standard, 2
b. Zinc or spelter, esp. that from China and the East Indies.
Standard, 2
A foam-producing agent used in fire extinguishers. Sinclair, 1
Sometimes used for piecework or contract work. Nelson
A pyroxene mineral, (Na,Al,Ca,Mg)Si2 O6 ; midway in
composition between diopside and jadeite; pea-green; massive; at Tuxtla,
Mexico. Formerly called diopside-jadeite. Also spelled tuxlite.
A tube or opening in a metallurgical furnace through which air is blown as
part of the extraction or refining process. In a blast furnace, the
tuyeres are water-cooled metal tubes which pass through the refractory
lining of the bosh (tube). Dodd
An arch in a blast furnace to admit a tuyere. See also:tuyere
Standard, 2; Fay
A refractory shape containing one or more holes through which air and
other gases are introduced into a furnace. ARI
A counterweighted furnace door, opening vertically. Also spelled tuille.
ASTM
a. See:divining rod
b. Thin strip of plastic fire clay used in ceramic modeling, esp. in
imitation basketwork. Standard, 2
Weave used in screens and filters, in which two or more warp threads
interweave one wood thread. Pryor, 3
The crystal axis about which one individual of a twin crystal may be
rotated (usually 180 degrees ) to bring it into coincidence with the other
individual. It cannot be coincident with the axes of twofold, fourfold, or
sixfold symmetry. Syn:twinning axis
See:dichroic colors
A composite of two or more crystal individuals having a definite
crystallographic relationship to each other. The orientation of one
individual may be the mirror image of the other across a twin plane, or an
orientation that can be derived by rotating the twin portions about a twin
axis, or some other rational twin law. Twinned individuals in a twin
crystal commonly show reentrant angles between crystal faces or on
cleavage planes. A twin crystal may exhibit symmetry higher than that of
its crystal individuals.