a. Like a star, with rays diverging from a center.
b. Said of a mineral, crystal, or gemstone that exhibits asterism; e.g.,
asteriated beryl. See:star
Quartz having whitish or colored radiations within the crystals.
See:star quartz
Asteriated yellow variety of corundum, wrongly called Oriental topaz.
Schaller
a. Starlike rays of light observed in some minerals when viewed from
certain directions, particularly if the mineral is cut en cabochon.
Minerals having this feature are called asteriated or star. Asteriated
beryl, chrysoberyl, crocidolite, emerald, quartz, ruby, and sapphire are
known. Hess
b. A starlike effect observed in certain minerals either by transmitted or
by reflected light. AGI
c. Elongation of Laue X-ray diffraction spots produced by stationary
single crystals as a result of internal crystalline deformation. The size
of the Laue spot is determined by the solid angle formed by the normals to
any set of diffracting planes; this angle increases with increasing
crystal deformation, producing progressively elongated (asteriated) spots.
Measurements of asterism are used as indicators of deformation in crystals
subjected to slow stress or to shock waves. CF:corundum cat's eye
A body of magma that was formed by melting in response to heat generated
by radioactive disintegration. AGI
The layer or shell of the Earth below the lithosphere, which has reduced
yield strength, permitting viscous or plastic flow under relatively small
stresses; it is a zone in which isostatic adjustments take place, magmas
may be generated, and seismic waves are strongly attenuated. It is a part
of the upper mantle. Syn:zone of mobility
AGI
A system based on proximate analysis in which coals containing less than
31% volatile matter on the mineral-matter-free basis (Parr formula) are
classified only on the basis of fixed carbon; i.e., 100% volatile matter.
They are divided into five groups: above 98% fixed carbon; 98% to 92%
fixed carbon; 92% to 86% fixed carbon; 86% to 78% fixed carbon; and 78% to
69% fixed carbon. The first three of these groups are called anthracites,
and the last two are called bituminous coals. The remaining bituminous
coals, the subbituminous coals, and the lignites are then classified into
groups as determined by the calorific value of the coals containing their
natural bed moisture; i.e., the coals as mined but free from any moisture
on the surface of the lumps. The classification includes three groups of
bituminous coals with moist calorific value from above 14,000 Btu/lb (32.5
MJ/kg) to above 13,000 Btu/lb (30.2 MJ/kg); three groups of subbituminous
coals with moist calorific value below 13,000 Btu/lb to below 8,300 Btu/lb
(19.3 MJ/kg); and two groups of lignitic coals with moist calorific value
below 8,300 Btu/lb. The classification also differentiates between
consolidated and unconsolidated lignites and between the weathering
characteristics of subbituminous and lignitic coals.
See also:coal classification systems
A blue to gray-violet variety of amphibole; at Wermland, Sweden. Locally
known as blue rhodonite. Syn:soda richterite
See:blodite.
An ornamental stone, consisting mainly of chromojadeite. From Manokwari,
New Guinea. English
a. A taste that puckers the mouth; descriptive of certain minerals, such
as alum. Fay
b. Causing contraction, shrinking, or puckering. Webster 3rd
c. Said of a clay containing an astringent salt.
a. A triclinic mineral, (K,Na)3 (Fe,Mn)7 Ti2 Si (sub
8) O24 (O,OH)7 ; forms a series with kupletskite.
b. A mineral group.
a. Without symmetry.
b. Said of mineral crystals having no center, plane, or axis of symmetry.
A vein with unlike mineral sequences on either side.
The class of crystal forms without any symmetry. Fay
A fold in which one limb dips more steeply than the other. If one limb is
overturned, the term "overturned fold" or "overfold" is used.
CF:symmetrical fold
The whole group of prototype atoms that, where repeated by the symmetry
operations of a space group, generate a crystal structure.
CF:unit cell
An orthorhombic mineral, 4[Cu2 Cl(OH)3 ] ; trimorphous with
paratacamite and botallackite; grass green, in fine crystal aggregates,
fibrous or columnar; a supergene mineral in oxidized zones of copper
deposits in desert regions; a source of copper. Syn:remolinite
Said of an unstratified mineral deposit. CF:eutaxic
A monoclinic mineral, Bi8 (AsO4 )3 O5 (OH)
5 ; yellow.
See:graded