A silicate of aluminum and barium, BaAl2 Si2 O8 . An
artificial feldspar, similar to anorthite, but containing barium instead
of calcium. Hexagonal prisms. Uniaxial, negative. English
See:digenite
A porcelain-white, hydrous acidic sulfosilicate of thorium with some
uranium, iron, and lead; isotropic. An alteration product of thorite. From
Hybla, ON, Can. English
See:vermilion
A quartz polymorph stable below 573 degrees C; a common constituent of
crustal rocks. Syn:low quartz
Colorless when pure; hexagonal; ZnS; mol wt., 97.43; sp gr, 3.98 to 4.1;
Mohs hardness, 3.5 to 4.0; luster, resinous; transformation temperature
from beta zinc sulfide to alpha zinc sulfide, 1,020+ or -5 degrees C:
sublimes at 1,180 degrees C or 1,185 degrees C; melting point, 1,850
degrees C (at 150 atm); insoluble in water and in acetic acid; and very
soluble in other acids. Occurs as the brownish-black mineral wurtzite,
which is unstable compared with its stable dimorph, the mineral sphalerite
(beta zinc sulfide), to which it inverts during alteration and from which
it is formed by heating sphalerite to the transformation temperature. Can
be crystallized from acid solutions above 250 degrees C.
See also:wurtzite; zinc sulfide. CF:beta zinc sulfide
Handbook of Chemistry and Physics, 2; Dana, 2
a. Pertaining to, characteristic of, or resembling the European Alps or
any lofty mountain or mountain system, esp. one modified by intense
glacial erosion. Spelled Alpine when referring specif. to European Alps.
AGI
b. Characteristic or descriptive of the mountainous regions lying between
timberline and snowline; said of the climate, flora, relief, ecology, etc.
Less strictly, pertaining to high elevations and cold climates.
AGI
c. A general term for topographical and structural features that resemble
in grandeur and complexity those of the European Alps, regardless of the
age or location of the mountains and features so described. AGI
See:pyrite
A coarse-grained variety of galena used by potters in preparing a green
glaze.
A variety of titanite containing yttria; found in Sweden.
Standard, 2
A triclinic mineral, BaCa(CO3 )2 ; pseudo-orthorhombic and
trimorphous with barytocalcite and paralstonite. Formerly called bromlite.
An isometric mineral, PbTe ; in veins with gold, sulfides, and other
tellurides.
Any change in the mineralogic composition of a rock brought about by
physical or chemical means, esp. by the action of hydrothermal solutions;
also, a secondary, i.e., supergene, change in a rock or mineral.
Alteration is sometimes considered as a phase of metamorphism, but is
usually distinguished from it because of being milder and more localized
than metamorphism is generally thought to be. AGI
A mineral that has undergone chemical change by geologic (esp. weathering
or hydrothermal) processes.
A rock that has undergone changes in its chemical and mineralogic
composition since its original formation. AGI
a. Said of a stone that has undergone chemical and/or mineralogical
changes under geologic processes.
b. Any stone of which the appearance, esp. the color, has been changed by
any artificial means whatsoever. For example, heat is often used to
improve or alter color. Such change may be either external or internal.
See also:treated stone; stained stone.
Arrangement in magnetic separator whereby ore travels alternately through
normal concentration and entropy fields, thus stirring attracted material
and shaking out entrained nonmagnetics. Pryor, 1
Current that will produce heat at the same rate as a direct-current
ampere, when flowing through a given ohmic resistance. Kentucky
A term used in the southwestern United States for a bluff, height, or
hill. Etymol: Sp., high ground. AGI
a. Any hydrous, alkali aluminum sulfate mineral, including kalinite,
potassium alum, sodium alum, mendozite, tschermigite, and lonecreekite.
Syn:potash alum
b. A former name for kalinite and potassium alum.
c. Any salts that are double sulfates of aluminum, chromium, iron, or
manganese and one of the alkali metals.