The production or formation of crystals. Adj: crystallogenic.
a. The science and the theory of the production of crystals.
Standard, 2
b. That branch of materials science that deals with the formation or
growth of crystals. CF:chemical mineralogy; experimental mineralogy;
phase equilibria.
A record, photographic or electronic, of crystal structure obtained by
means of X-ray diffraction. CF:Laue diagram; Laue photograph;
powder pattern.
a. Three axes intersecting at right angles, the vertical one being the x
axis and the two horizontal ones the y and z. The position of a crystal
face is defined by the ratio of its intercepts with these axes.
Pryor, 3
b. The three noncoplanar reference vectors used to describe crystal
properties. Depending upon the crystal system, these axes are not
necessarily orthogonal nor of equal length, with angle alpha between axes
b and c, beta between a and c, and gamma between a and b. Axes of equal
length are labeled a. Where one axis is unique (hexad, tetrad, triad, or
monad), convention sets it vertical and labels it c. A unique diad may be
labelled c (first crystallographic setting) or b (second setting,
preferred by mineralogists). By convention positive b is plotted to the
right and positive a toward the observer. Some crystal classes with a
unique triad may be referred to a set of three nonorthogonal axes of equal
length at internal angle alpha, i.e., rhombohedral coordinates ar .
In the case of a unique triad or hexad, a fourth redundant axis a3
may be added for convenience. CF:axis; coordinate system;
crystal systems; fold.
See:crystal axis
a. Refers to directions in the various crystal systems that correspond
with the growth of the mineral and often with the direction of one of the
faces of the original crystal itself.
b. Vectors referred to as crystallographic axes. Because of crystalline
periodicity, significant directions within a crystal are determined by the
rational intercepts with the crystallographic axes and may be rendered in
terms of Miller indices enclosed in brackets, e.g., [hkl] or [hkil].
a. Any set of parallel and equally spaced planes that may be supposed to
pass through the centers of atoms in crystals. As every plane must pass
through atomic centers and no centers must be situated between planes, the
distance between successive planes in a set depends on their direction in
relation to the arrangement of atomic centers. CTD
b. Those planes that make rational intercepts with crystallographic axes
and that may be noted by their intercept reciprocals, the Miller indices
enclosed in parentheses, i.e., (hkl) or (hkil). Such planes may represent
crystal faces, cleavage planes, twin planes, lattice points, or planes of
atomic particles in a crystal structure.
a. Any of the major units of crystal classification, embracing one or more
symmetry classes. CTD
b. See:crystal system; holohedral.
A texture of mineral deposits formed by replacement or exsolution, in
which the distribution and form of the inclusions are controlled by the
crystallography of the host mineral. AGI
a. The study of crystals, including their growth, structure, physical
properties, and classification by form. AGI
b. The science of the geometry of crystals and crystalline materials that
results from symmetry generated by the periodicity of their atomic
particles. See also:symmetry
a. Having some or all of the properties of a crystal.
b. A microscopic crystal that, when examined under a microscope, polarizes
light but has no crystal outline or readily determinable optical
properties. CF:crystallite; microlite. AGI
The science of crystals and crystalline materials. It embraces
crystallography and crystallogeny.
The emission of light by a substance during its crystallization.
AGI
A descriptive term applied to igneous rocks with an orbicular texture in
which early phenocrysts form the nuclei of the orbicules (Eskola, 1938).
CF:isothrausmatic; heterothrausmatic; homeothrausmatic. AGI
Any substance possessing crystal structure but no definite geometric form
visible to the unaided eye. Also known as crystalline material.
Partially crystallized magma; an aggregate of solid crystals lubricated by
compressed water vapor. AGI
a. The science that treats of the transmission of light in crystals.
Fay
b. The study and characterization of the optical properties of crystalline
materials. Because each mineral species is a unique combination of
chemistry and crystal symmetry, use of optical properties of minerals,
both opaque and transparent, for their characterization and identification
is a well-developed art.
A space lattice of a crystal structure. See also:space lattice
Hackh
The recovery of the original properties in a crystal that has been
distorted by stress resulting from continued relief from stress, heating,
or decrease in the speed of deformation. Knopf
A point contact between a metal and a crystal (such as copper and galena),
or between two crystals (such as zincite and bornite). It has marked
unidirectional conductivity. CTD
a. Trade term for fourth-grade diamonds; colorless diamonds. Hess
b. Atomic structures with long-range order. (Euhedral surfaces are not
required.) Van Vlack
c. Geometrical forms of planar faces assumed by minerals and other
crystalline materials when grown under appropriate conditions.
d. Australian syn. for drill diamonds.