a. A sandstone in which the quartz grains have been enlarged by deposition
of silica so that the grains show regenerated crystal facets and sometimes
nearly perfect quartz euhedra. Crystal sandstones of this nature sparkle
in bright sunlight. AGI
b. A sandstone in which calcite has been deposited in the pores in large
patches or units having a single crystallographic orientation, resulting
in a poikiloblastic or luster-mottling effect. In some rare sandstones
with incomplete cementation, the carbonate occurs as sand-filled
scalenohedra of calcite--sand crystals. See also:sand crystal
AGI
See:crystal settling
In a magma, the sinking of crystals because of their greater density,
sometimes aided by magmatic convection. It results in crystal
accumulation, which develops layering. CF:crystal flotation
Syn:crystal sedimentation
The replacement of one chemical element by others in a crystal structure
without changing its symmetry. Syn:solid solution
The separation, by any process, of crystals from a magma, or of one
crystal phase from another during crystallization of the magma.
AGI
An X-ray spectrometer employing a crystal grating. Webster 3rd
a. The periodic or repeated arrangement of atoms in a crystal. AGI
b. The arrangement in most pure metals may be imitated by packing spheres,
and the same applies to many of the constituents of alloys. CTD
c. The periodic array of atomic particles as represented by their
symmetrical disposition. Syn:crystalline structure
a. A classification of crystals based on the intercepts made on the
crystallographic axes by certain crystal faces (or bounding planes).
Syn:crystallization systems
CMD
b. The six main symmetry groups into which all crystals, whether natural
or artificial, can be classified. See also:symmetry
c. The classification of point groups (and their associated crystal
classes) and space lattices into seven (or six) symmetry systems; e.g.,
isometric (three equal orthogonal crystal axes), hexagonal (a unique
hexad), trigonal (a unique triad), tetragonal (a unique tetrad),
orthorhombic (three orthogonal diads), monoclinic (one diad inclined to an
axial plane), and triclinic (no symmetry higher than a center) systems. An
alternative classification of six systems assigns hexagonal and
rhombohedral divisions to the hexagonal system with a different assignment
of point groups having unique triads and hexads. CF:tetragonal
An indurated deposit of volcanic ash dominantly composed of intratelluric
crystals and crystal fragments. CF:tuff; crystal-vitric tuff;
lithic tuff; vitric tuff.
A tuff that consists of fragments of crystals and volcanic glass.
CF:crystal tuff; vitric tuff. AGI
Crystal modification of quartz, which is formed by heating clay silica
bodies at temperatures above 1,100 degrees C. Heating increases the
thermal expansion and decreases the danger of crazing. Rosenthal
A thick-wall steel collar, the inside surface of which is tapered to fit
two serrated-face taper sleeves. The assembly may be fitted at any point
over a casing or pipe and serves as a drive collar in sinking casing or
pipe by driving and chopping. Also called self-tightening jar collar;
self-tightening jar coupling; Simmons jar block, Simmons jar collar.
Long
Trade name; a refractory nozzle for steel pouring designed to give a
constant teeming rate (therefore, the name). The nozzle consists of an
outer fireclay shell and a refractory insert of different composition.
Strictly speaking, the term refers to a particular type of insert
developed for the teeming of free cutting steels. Dodd
An orthorhombic mineral, CuFe2 S3 ; dimorphous with
isocubanite. Formerly called chalmersite.
A niche cut in the rib or wall of an underground mine for the storage of
explosives or detonators.
a. Scot. A ventilating furnace in a mine.
b. A relatively rare crystal form of diamond having six equal-area faces
at right angles to each other. Long
c. A rectangular prism having squares for its ends and faces.
Jones, 2
d. A crystal form of six equivalent (not necessarily square) and mutually
perpendicular faces, with indices of 100. AGI
e. A hexahedron, a crystal form of the isometric system consisting of six
mutually orthogonal planar faces. Conditions of growth may yield crystal
faces that are not perfectly square, but are at mutual right angles.
f. A diamond in cube form.
g. Dice, e.g., pyrite cubes known locally as devil's dice.
h. Pseudocubic forms, e.g., quartz rhombohedra with faces at near right
angles, tetragonal prisms capped by a basal pinacoid, orthorhombic prisms
or domes terminated by a pinacoid, or three orthorhombic pinacoids of
nearly equal areas.
Eng. An arsenate of iron, KFe4 (AsO4 )3 (OH)4
.6-7H2 O , of an olive-green to yellowish-brown color, and
occurring commonly in cubes with the copper ores of Cornwall.
Syn:pharmacosiderite
Gunpowder made in large cubical grains and burning more slowly than the
small or irregular grains. Fay
a. Having the form of a cube, as a cubic crystal; or referring to
directions parallel to the faces of a cube, as cubic cleavage.
See also:cubic system
b. Crystal cleavage with three planes at mutual right angles.
c. An alternate name for the isometric crystal system.
See also:isometric
d. In crystal structures, a cation coordination of six equidistant anions.
a. Equally good cleavage in three mutually perpendicular directions.
Fay
b. Mineral cleavage parallel to the faces of a cube, e.g., in galena or
halite.