Former name for argentite.
Former name for pyrargyrite.
A nickel mineral between nickeline and breithauptite in composition.
arithmetic-mean particle diameter
A measure of the average particle size obtained by summing the products of
the size-grade midpoints times the frequency of particles in each class,
and dividing by the total frequency. AGI
A deep-red or ruby-colored variety of pyrope garnet of igneous origin,
Southwestern United States.
a. A hexagonal mineral, Fe2 Ti3 O9 ; in irregular
metallic steel-gray masses in pegmatite veins near Hackberry, AZ. Formerly
called pseudorutile.
b. A mixture of hematite, rutile, ilmenite, and anatase. AGI
c. An ore of micaceous iron, silver iodide, gold, iron sulfides, and
antimony in a vein in Yavapai County, AZ. AGI
d. A hypabyssal rock with 80% quartz, 18% alkali feldspar, and accessory
mica and apatite in Arizona (not a rock name in the IUGS classification).
AGI
A diamond from Murfreesboro, AR.
A variety of novaculite found in the Ouachita Mountains of western
Arkansas. Also, a whetstone made of Arkansas stone.
See also:novaculite
A brilliant, iron-black variety of brookite from Magnet Cove, AR.
Fay
A feldspar-rich sandstone, typically coarse-grained and pink or reddish,
that is composed of angular to subangular grains that may be either poorly
or moderately well sorted; usually derived from the rapid disintegration
of granite or granitic rocks, and often closely resembles granite; e.g.,
the Triassic arkoses of the Eastern United States. Quartz is usually the
dominant mineral, with feldspar (chiefly microcline) constituting at least
25%. Cement (silica or calcite) is commonly rare, and matrix material
(usually less than 15%) includes clay minerals (esp. kaolinite), mica, and
iron oxide; fine-grained rock fragments are often present. Arkose is
commonly a current-deposited sandstone of continental origin, occurring as
a thick, wedge-shaped mass of limited geographic extent (as in a fault
trough or a rapidly subsiding basin); it may be strongly cross-bedded and
associated with coarse granite-bearing conglomerate, and it may denote an
environment of high relief and vigorous erosion of strongly uplifted
granitic rocks in which the feldspar was not subjected to prolonged
weathering or transport before burial. Arkose may also occur at the base
of a sedimentary series as a thin blanketlike residuum derived from and
resting on granitic rock. Etymol: French, probably from Greek archaios,
ancient, primitive. Syn:arkosic
subarkose. Also spelled arcose. AGI
See:arkosite
Having the character of arkose.
A sandstone with considerable feldspar, such as one containing minerals
derived from coarse-grained quartzo-feldspathic rocks (granite,
granodiorite, gneiss) or from highly feldspathic sedimentary rocks;
specif. a sandstone containing more than 25% feldspar and less than 20%
matrix material of clay, sericite, and chlorite. See also:arkosite
AGI
A quartzite with a notable amount of feldspar. Syn:arkose quartzite
See also:arkosic sandstone
The inclined member or leg of a set or frame of timber.
A trigonal mineral, Mn26 As18 O50 (OH)4 (CO
3 ) ; black; near Laangban, Sweden.
A conveyor consisting of an endless belt, or one or more chains, to which
are attached projecting arms, or shelves, for handling packages or objects
in a vertical or inclined path.
a. A hexagonal mineral, BaCa2 Al6 Si9 O30 .2H
2 O ; osumilite group.
b. Former name for azurite, Armenian stone.
An outer cable covering that may be either metallic or nonmetallic.
An apron in which each pan is provided with a separate wearing plate.
A cable that is wrapped with metal, usually steel wires or tapes,
primarily for physical protection. See also:cable