See:azurmalachite
Chalcedony colored blue by chrysocolla; and used as a gemstone.
Syn:azurchalcedony
An intimate mixture or intergrowth of azurite and malachite, commonly
massive and concentrically banded; used as an ornamental stone.
Syn:azure malachite; azurite malachite.
S. Afr. A boundary mark.
Dry-grinding mill in which steel balls rotate in a horizontal ring,
through which the feed is worked downward. Pryor, 3
A variety of quartz, named for the fancied resemblance of the crystal to
the successive tiers of the Tower of Babel. Syn:Babylonian quartz
See:Babel quartz
a. A variety of amber. Tomkeieff
b. A variety of quartz in Baja California, Mex.
a. A system of joints in coal oblique to the bedding, at an angle of about
35 degrees to 75 degrees . Backs are usually perfectly tight and have
polished cheeks which suggest a certain amount of movement. Back may be
applied to the principal cleat. See also:backs; cleat.
b. The roof or upper part of any underground mining cavity.
c. The ore between a level and the surface, or between two levels.
See also:back of ore
d. That part of a lode which is nearest the surface relative to any
working part of a mine, thus the back of the level or stope is that part
of the unstoped lode which is above. See also:back of lode
e. A joint, usually a strike joint, which is perpendicular to the
direction of working.
f. As applied to an arch, the outer or upper surface.
g. The pavilion of a gemstone.
Front-end equipment fitted to an excavator, comprising a jib with an arm
and bucket. Although designed primarily for vertically sided trenching, it
is also useful for bulk excavation below track level. Nelson
back and underhand stoping milling system
See:combined overhand and underhand stoping
A concealed arch carrying the backing or inner part of a wall where the
exterior facing material is carried by a lintel. ACSG, 1
a. A type of self-acting incline in a mine. A balance car is attached to
one end of a rope, and a carriage for the mine car is attached to the
other end. A loaded car is run on the carriage and is lowered to the foot
of the incline, raising the balance car. The balance car in its descent
raises the carriage when the carriage is loaded only with an empty car.
Fay
b. The means of maintaining tension on a rope transmission or haulage
system, consisting of the tension carriage, attached weight, and
supporting structure. Fay
See:backlash
Rock broken beyond the limits of the last row of holes marking the outer
boundary in a blast.
a. A ripper engaged in taking down the roof in roadways some distance back
from the face. Syn:second ripping
b. Back ripper.
General work performed behind the working faces, as opposed to work done
at the faces. This is commonly referred to as "outby work."
Eng. A temporary shaft lining of bricks laid dry, and supported at
intervals upon curbs. When the stonehead has been reached, the permanent
masonry lining is built upon it inside of the back casing.
A stripping method using two draglines, one of which strips and casts the
overburden while the other recasts a portion of the overburden.
Woodruff
Scot. Coal that miners are allowed to carry home.
Scot. Working away the pillars that are left when mining coal inby.
Robbing pillars; back working. See also:back work