Said of a mineral deposit or enrichment of mingled hypogene and supergene
solutions; also, said of such solutions and environment. CF:hypogene;
supergene. AGI
Group name for brown coals. Tomkeieff
A monoclinic mineral, Na2 Ca2 [Al2 Si3 O (sub
10) ]3 .8H2 O ; zeolite group; pseudo-orthorhombic; in
cavities in basalt and andesite, geodes, and hydrothermal veins.
Syn:cotton stone; winchellite.
Microcline intermediate in structural state between orthoclase and maximum
microcline. Syn:intermediate microcline
The last-formed interstitial material between the larger mineral grains in
an igneous rock or in a microcrystalline groundmass. CF:groundmass
Said of a hydrothermal mineral deposit formed at considerable depth and in
the temperature range of 200 to 300 degrees C. Also, said of that
environment. CF:hypothermal deposit; epithermal; leptothermal;
telethermal; xenothermal. AGI
A mineral deposit formed at moderate temperature and pressure, in and
along fissures or other openings in rocks, by deposition at intermediate
depths, from hydrothermal fluids. Mesothermal deposits are believed to
have formed mostly between 175 degrees C and 300 degrees C at depths of
4,000 to 12,000 ft (1,220 to 3,660 m). Many valuable metalliferous
deposits of western North America are of this type. Stokes
An era of geologic time, from the end of the Paleozoic to the beginning of
the Cenozoic, or from about 225 million years to about 65 million years
ago. AGI
According to Grubenmann's classification of metamorphic rocks (1904), the
intermediate-depth zone of metamorphism, which is characterized by
temperatures of 300 to 500 degrees C and moderate hydrostatic pressure and
shearing stress. Modern usage stresses temperature-pressure conditions
(medium to high metamorphic grade) rather than the likely depth of zone.
CF:katazone; epizone. AGI
A triclinic mineral, Ca2 (Fe,Mn)(PO4 )2 .2H2 O;
fairfieldite group. Syn:neomesselite; parbigite. (Not mesolite.)
Port. Mine boss. Hess
a. In petrology, indicates a metamorphosed protolith.
b. In mineralogy, indicates a mineral species that is a dehydration
product of another mineral species or is a polymorph.
A prefix that, when used with the name of a sedimentary or igneous rock,
indicates that the rock has been metamorphosed, e.g., metabasalt.
CF:cata-; meso-. AGI
A monoclinic mineral, Al4 (SO4 )6 .27H2 O .
See also:alunogen
The rank of coal, within the anthracite class of Classification D-388,
such that, on the dry and mineral-matter-free basis, the volatile matter
content of the coal is equal to or less than 2% (or the fixed carbon is
equal to or greater than 98%), and the coal is nonagglomerating.
ASTM
An argillite that has been metamorphosed. AGI
Arkose that has been welded or recrystallized by metamorphism so that it
resembles a granite or a granitized sediment. CF:recomposed granite
AGI
a. A tetragonal mineral, Ca(UO2 )2 (PO4 )2 .
2-6H2 O ; yellow; an alteration product of uraninite and other
uranium-bearing minerals.
b. The mineral group abernathyite, bassetite, chernikovite,
meta-ankoleite, meta-autunite, metaheinrichite, metakahlerite,
metakirchheimerite, metalodevite, metanovacekite, metatorbernite,
meta-uranocircite, meta-uranospinite, metazeunerite, sodium uranospinite,
and uramphite.
A collective term, first used by Finnish geologists, for metamorphosed
mafic rock that has lost all traces of its original texture and mineralogy
owing to complete recrystallization. AGI
a. Metamorphosed, altered, or somewhat indurated bentonite; characterized
by clay minerals (esp. illite) that no longer have the property of
absorbing or adsorbing large quantities of water; nonswelling bentonite,
or bentonite that swells no more than do ordinary clays. The term has been
applied to certain Ordovician clays of the Appalachian region and upper
Mississippi River Valley. See also:potassium bentonite
b. A mineral of the montmorillonite group with SiO2 layers in the
montmorillonite structure. AGI
Hard black lustrous variety of hydrocarbon found in proximity of igneous
intrusions. Tomkeieff