The term corundum is now applied to the coarser and less transparent kinds of the stone, which have been used as a polishing material from time immemorial. The granular variety known as emery is largely mixed with iron ores, and is far inferior to the transparent and purer varieties as an abrading agent. It is always of a blackish or dark-gray hue, and is often mistaken for iron ore. Asia Minor furnishes nearly all of the emery used in the arts. It is found there in masses or bowlders, either free or in granular limestone. In the United States it is found along the gold belt in the Southern States; and in Chester, a town of Massachusetts, it occurs in a large and valuable vein associated with diaspore, ripidolite, etc., which generally accompany it. At this mine at Chester, translucent sapphires of bi-pyramidal form are sometimes found. Dr. C. J. Jackson found one small blue crystal quite transparent and doubly terminated. The corundum belt of the United States has been traced, with wide intervals, however, from Philadelphia to Northern Georgia. All along this distance of several hundred miles, masses of corundum, more or less transparent, have been found during the past forty years, but active search failed to reveal the mineral in its matrix. A few years ago exploration in the extreme southwestern part of North Carolina discovered the long-looked-for corundum _in situ_. It was found on the side of a mountain, in a mica-like substance called ripidolite. The corundum from this locality appears in geodes and also in well-marked crystals, ranging from small size to even the weight of three hundred pounds. It is often of perfect transparency, but may be translucent or opaque. The transparent crystals and masses, although possessing limpidity, are traversed in all directions with cleavage planes, which prevent their use in ornamentation. The colors are also irregularly distributed in patches, clouds, or in thin veneers; many specimens have been seen of variegated hues,--red, white, yellow, and blue,--and even the whole of these colors have been seen in a single specimen. From the great number of specimens submitted to our examination we have no hesitation in saying that gems cannot be quarried at will from these mines. The inequality of color and the frequency of cleavage planes will forbid. Small gems of few grains weight may be cut from some of the transparent masses if the clear portions are selected with care, and cut with that skill which is required in the shaping of gems whose color is unequally distributed. But it is doubtful if fine gems are found in this formation, for the conditions which deposited the corundum here, and the more perfect specimens in the true gem strata elsewhere, are quite different.