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;
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.
Dictionary of Mining, Mineral, and Related Terms