A Spanish magnetite with a siliceous gangue. Osborne
a. A metamorphic rock composed essentially of calcite, dolomite, or a
combination of the two, with a fine- to coarse-grained crystalline
texture.
b. In commerce, any crystalline carbonate rock that will take a polish,
including true marble, certain coarse-grained limestones, alabaster, and
onyx.
c. See:verde antique
A toothless blade fitted at the back with a block handle, used with sand,
for cutting slabs of marble into pieces. Fay
A toothless blade used with sand in marble cutting. Standard, 2
An etchant for stainless steels, consisting of 4 g of copper sulfate in 20
mL of hydrochloric acid and 20 mL of water. Osborne
a. White iron pyrites, FeS2 , the orthorhombic dimorph of pyrite,
having a lower specific gravity, less stability, and a paler color. Often
called white iron pyrites, coxcomb pyrites, and spear pyrites. AGI
b. In the gemstone trade, marcasite is either pyrite, polished steel
(widely used in ornamental jewelry in the form of small brilliants), or
even white metal. CTD
c. An orthorhombic mineral, FeS2 ; dimorphous with pyrite;
metallic; bronze-yellow to white; an authigenic or supergene mineral from
acid solutions. Syn:white iron pyrites; white pyrite; cockscomb pyrite;
spear pyrite; lamellar pyrite.
d. The mineral group ferroselite, frohbergite, hastite, kullerudite,
marcasite, and mattagamite.
e. A gemstone with a metallic luster, esp. pyrite, but including polished
steel and white metal. Syn:radiated pyrite
A patented shaker screen with a nonharmonic or quick-return motion.
Zern
A ball mill in which a vertical-grate diaphragm is placed near the
discharge end. Between this perforated diaphragm and the end of the tube,
there are arranged screens for sizing the material, oversize being
returned for further grinding while undersize is discharged.
Liddell
York and Lanc. Spherical ferruginous concretions. CF:caballa ball
Arkell
Obsidian that occurs as rounded to subangular bodies, usually less than 2
in (5.1 cm) in diameter and having indented surfaces. These bodies occur
in masses of perlite and are of special interest because of their low
water content as compared with the surrounding perlite. The name is from
the Marekanka River, Okhotsk, Siberia, Russia. AGI
a. A beadlike string of globulites, commonly found in glassy igneous
rocks. AGI
b. A monoclinic mineral, 4[CaAl2 (Al2 Si2 O10
)(OH)2 ] ; mica group; forms brittle folia; associated with
corundum. Syn:brittle mica; pearl mica.
A pearly variety of muscovite.
A triclinic mineral, Pb(Ca,Mn)2 Si3 O9 .
a. A magmatic segregation at the bottom and periphery of an intrusive
rock; e.g., nickel-copper-sulfide deposits at Sudbury, ON, Canada.
b. Marginal ore deposit.
A fracture, bordering an igneous intrusion, that has become filled with
magma. AGI
A deposit near the lower limit of commercial workability.
Bateman, 2
That part of the reserve base that, at the time of determination, borders
on being economically producible. Its essential characteristic is economic
uncertainty. Included are resources that would be producible, given
postulated changes in economic or technologic factors. USGS, 2
An adjacent sea that is widely open to the ocean.
See also:adjacent sea
A thrust fault along the margin of an intrusive that dips toward the
intrusive. AGI
See:trench
An early name for both mica and selenite (gypsum).