See:cordierite
An orthorhombic mineral, (Y,Ca,Ce,U,Th)(Ti,Nb,Ta)2 O6 ;
black; in granite pegmatites. Formerly spelled polykras.
A mineral specimen composed of an assemblage of individual crystals of
various crystallographic orientations. See also:glomerocryst; syntaxy.
An aggregate of crystals of the same species.
An isometric mineral, NiNi2 S4 ; linnaeite group; easily
confused with violarite.
a. Resulting from more than one process of formation, derived from more
than one source, or originating or developing at various places and times;
e.g., said of a mountain range resulting from several orogenic episodes.
AGI
b. Consisting of more than one type of material, or having a heterogeneous
composition; e.g., said of a conglomerate composed of materials from
several different sources. CF:monogenetic
A plane figure bounded by straight lines. Jones, 2
A two-dimensional form having more than four regular straight sides.
An ore-reserve computation method in which an assumption is made that the
area of influence of each drill hole extends halfway to the neighboring
drill holes. Therefore, thickness and grade must vary uniformly in
opposite directions and in such cases errors tend to be compensating.
Where the thickness and grade vary in the same direction, the errors will
accumulate and cause erroneous results. Krumlauf
A triclinic mineral, K2 Ca2 Mg(SO4 )4 .2H (sub
2) O ; bitter tasting; varicolored; occurs in salt deposits in Texas, New
Mexico, and Germany.
See:polycrase
a. A compound formed by the union of two or more molecules of the same
simple substance. Standard, 2
b. In the plural use, compounds identical in composition but which vary in
molecular weight, such as ethylene (ethene), Ch2 :Ch2 ;
propylene (propene), CH3 CH:CH2 ; and butylene (butene), CH
3 CH2 CH:CH2 . Standard, 2
Union of two or more molecules of given structure to form a new compound
with the same elemental proportions but with different properties and a
higher molecular weight. Pryor, 3
To chemically combine small molecules into larger molecules; to undergo
polymerization.
A sulfide deposit rich in copper, zinc, lead, silver, or gold, which forms
as a result of hydrothermal activity in the vicinity of mid-ocean
spreading centers or tectonically active basins. The first discovery of
these deposits was from the French submersible Cyana, in 1979, during a
joint international biological investigation of thermal springs on the
deep seabed. The term derives from the French "sulfides polymetalliques."
An orthorhombic mineral, (Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4 ; radioactive;
in syenites and granite pegmatites. Also spelled polymignyte.
The characteristic of a chemical compound to crystallize in more than one
crystal class; e.g.: (1) kyanite, andalusite, and sillimanite; (2) quartz,
tridymite, cristobalite, coesite, and stishovite. Allotropy refers specif.
to chemical elements crystallizing in more than one class; e.g., graphite,
diamond, chaoite, and lonsdaleite. Polymorphism limited to two or three
crystal classes is dimorphism or trimorphism, respectively. Individual
species are polymorphs (dimorphs, trimorphs). Polytypism refers to
variable stacking of identical layer structures in different crystal
classes. Adj: polymorphic (dimorphic, trimorphic). Adv: polymorphous
(dimorphous, trimorphous). Syn:pleomorphism
trimorphism; isomorphism; isotypy; polysyngony. See also:allotropic
Variety of nigritite found in a finely dispersed state in argillaceous
rocks. CF:keronigritite; humonigritite. Tomkeieff
A montmorillonoid clay mineral in soils. Spencer, 6
In electricity, having or producing two or more phases, such as a
polyphase current. Syn:multiphase
Having a texture consisting of numerous small grains; said of minerals.
Standard, 2