a. A metamorphosed limestone; a marble formed by recrystallization of
limestone as a result of metamorphism. AGI
b. A calcarenite with crystalline calcite cement formed in optical
continuity with crystalline fossil fragments by diagenesis. AGI
c. A limestone formed of abundant calcite crystals as a result of
diagenesis; specif. a limestone in which calcite crystals larger than 20
mu m in diameter are the predominant components. Examples include the
crinoidal limestones whose fragments have been enlarged by growth of
calcite. CF:marble
A term used to distinguish all the varieties of quartz which are not
cryptocrystalline, such as rock crystal, amethyst, citrine, cairngorm,
rose quartz, tiger eye, etc.
a. An inexact, but convenient term designating an igneous or metamorphic
rock, as opposed to a sedimentary rock. AGI
b. A rock consisting wholly of relatively large mineral grains, e.g., a
plutonic rock, an igneous rock lacking glassy material, or a metamorphic
rock. AGI
c. The term has also been applied to sedimentary rocks, e.g., some
limestones, that are composed of coarsely crystalline grains or exhibit a
texture formed by partial or complete recrystallization. AGI
This type of tonstein contains vermicular, prismatic, or tabular kaolinite
crystals and may be either light or dark in color according to the
proportion of contained carbonaceous matter. Occasionally granular
kaolinite may also be recognized. The crystals lie embedded in either a
finely crystalline or cryptocrystalline kaolinite groundmass. IHCP
a. The degree to which a rock (esp. an igneous rock) is crystalline
(holocrystalline, hypocrystalline, etc.). AGI
b. The degree to which the crystalline character of an igneous rock is
developed (e.g., macrocrystalline, microcrystalline, or cryptocrystalline)
or is apparent (e.g., phaneritic or aphanitic). AGI
a. A broad term applied to a minute body of unknown mineralogic
composition, or crystal form that does not polarize light. Crystallites
represent the initial stage of crystallization of a magma or of a glass.
Syn:crystallitic
b. Very small crystals in a mass or matrix.
c. A nucleus from which a crystal may grow.
d. Minute spots of double refraction in a glassy matrix.
Of, pertaining to, or formed of, crystallites.
a. The process through which crystalline phases separate from a fluid, a
viscous, or a dispersed state (gas, liquid solution, or rigid solution).
Holmes, 1
b. The process of crystallizing. A form of body resulting from
crystallizing. Webster 3rd
c. Formation of crystalline phases during the cooling of a melt or
precipitation from a solution.
crystallization differentiation
The progressive change in composition of the liquid fraction of a magma as
a result of the crystallization of mineral phases that differ in
composition from the magma. AGI
a. The interval of temperature (or less frequently pressure) between the
formation of the first crystal and the disappearance of the last drop of
liquid from a magma on cooling. It usually excludes the late-stage aqueous
fluids. AGI
b. When referring to a given mineral, the range or the ranges of
temperatures over which that particular phase is in equilibrium with
liquid. In the case of equilibria along reaction lines or reaction
surfaces, crystallization intervals, as thus defined, include temperature
ranges in which certain solid phases are actually decreasing in amount
with decrease in temperature. Syn:freezing interval
A small particle of any kind around which crystals begin to form when a
substance crystallizes.
a. The 32 possible crystal groups, distinguished from one another by their
symmetry, are classified under 6 systems, each characterized by the
relative lengths and inclinations of the assumed crystallographic axes.
These are isometric, tetragonal, hexagonal, orthorhombic, monoclinic, and
triclinic. Fay
b. See:crystal systems
a. To cause to form crystals or to assume crystalline form; esp. to cause
to assume perfect or large crystals. To cause to take a fixed and definite
form. To become converted into crystals. To solidify by crystallizing. To
deposit crystals. To become fixed and definite in form.
Webster 3rd
b. Any process by which matter becomes crystalline from a noncrystalline
state. Also spelled "crystalize."
a. The potentiality, or the expansive force, by which a mineral tends to
develop its own crystal form against the resistance of the surrounding
solid mass. This may be a differential force that causes the crystal to
grow preferentially and more rapidly in one crystallographic direction
than in another.
b. Expulsion of foreign constituent from a growing crystal by diffusion or
mechanical displacement.
c. Expansion resulting from a crystal phase that is less dense than its
noncrystalline melt phase, e.g., freezing water splitting rock or bursting
pipes.
A crystal of a mineral produced entirely by metamorphic processes.
See also:idioblast; xenoblast. Adj: crystalloblastic. AGI
Deformation by metamorphic recrystallization. Knopf
a. Pertaining to a crystalloblast. AGI
b. Said of a crystalline texture produced by metamorphic recrystallization
under conditions of high viscosity and directed pressure, in contrast to
igneous rock textures that are the result of successive crystallization of
minerals under conditions of relatively low viscosity and nearly uniform
pressure (Becke, 1903). CF:homeoblastic; heteroblastic. AGI
c. A metamorphic texture wherein one or more mineral species grows
substantially larger than the rock matrix, e.g., garnet schist.
CF:porphyroblastic; granoblastic.
d. A crystalline texture owed to metamorphic recrystallization. A
characteristic of this texture is that the essential constituents are
simultaneous crystallizations and are not found in sequence, so that each
may be found as inclusions in all the others.
An arrangement of metamorphic minerals in order of decreasing form energy,
so that crystals of any of the listed minerals tend to assume idioblastic
outlines at surfaces of contact with simultaneously developed crystals of
all minerals occupying lower positions in the series. AGI
An element essential to the composition and the structure of a mineral.
AGI