a. A mixture of a hydromica and corundum.
b. A potassian variety of margarite.
A heavy-fluid coal-cleaning process in which a calcium chloride solution
having a specific gravity of approx. 1.4 is used for the separation, which
takes place in a cylindrical tank 6 to 10 ft (1.8 to 3 m) in diameter with
a conical bottom, the total height being nearly 30 ft (9.1 m). The cleaned
coal rises to the top where it is removed by a chain scraper and delivered
to draining towers. Gaudin, 1
A dose of ionizing radiation sufficient to cause death. Median lethal dose
(abbreviated MLD or LD50 ) is the dose required to kill half of the
individuals in a group similarly exposed within a specified period of
time. The median lethal dose for humans is about 400 rads. Lyman
Eng. The recessing of supports into the floor, side, or roof. SMRB
A triclinic mineral, (NH4 )3 H(SO4 )2 ; a
decomposition product of pyrite in coal.
In the stonework industry, a person who cuts incised or raised letters and
simple designs on monumental stones with pneumatic and hand tools. Also
called letter cutter; letterer. DOT
An igneous rock with sheath and core structure giving the appearance of
letters on its surface.
See:cyanotrichite; velvet copper ore.
A pale iron-poor variety of clinochlore.
A tetragonal mineral, 16[KAlSi2 O6 ] ; a pseudocubic
feldspathoid; forms white to gray trapezohedra in potassium-rich,
silica-poor lavas. Syn:amphigene; grenatite; white garnet; vesuvian.
CF:pseudoleucite
A fine-grained or porphyritic extrusive or hypabyssal igneous rock chiefly
composed of pyroxene (esp. titanaugite) and leucite, with little or no
feldspar and without olivine. AGI
See:trapezohedron
A porphyritic extrusive rock composed chiefly of leucite, nepheline, and
clinopyroxene. CF:haueynophyre
See:olivinite
Light-colored; applied to igneous rocks that are relatively poor in mafic
minerals. The percentage of mafic minerals necessary for a rock to be
classified as leucocratic varies among petrologists, but is usually given
as less than 30% to 37.5%. CF:melanocratic; mesocratic. Noun,
leucocrate. Syn:light-colored
See:fairfieldite
A loamlike substance, between a resin and wax in character; C50 H
84 O3 ; very impure and sandy as found in a brown coal at
Gesterwitz, near Weissenfels, Germany. It crystallizes in white needles
from ether and boiling absolute alcohol, and melts above 100 degrees C.
AGI
A green to pale-yellow sodium calcium silicate containing beryllium. One
of the sources of beryllium. See also:leucophanite
A triclinic mineral, (Na,Ca)2 BeSi2 (O,OH,F)7 ;
pseudo-orthorhombic; a source of beryllium. Syn:leucophane
A monoclinic mineral, Mn7 (SiO4 )3 (OH)2 ;
humite group; pseudo-orthorhombic; purple-pink to raspberry-red; in veins
associated with manganese ore deposits.
A variety of muscovite. Dana, 1