168 CORUNDUM, ITS OCCURRENCE AND DISTRIBUTION. 
SUGGESTIOIS^S TO PROSPECTORS FOR CORUNDUM. 
Many of the early discoveries of corundum were made as discov- 
eries of many of the other minerals have been made — that is, by the 
accidental finding of fragments, which led to systematic search, 
resulting in many cases in the location of extended deposits. The 
presence of other minerals associated with corundum are important 
indications of its existence. Thus the presence of margarite at the 
old iron mine at Chester, Mass., was to Prof. A. T. Jackson, who was 
familiar with its occurrence, an indication that corundum would be 
found. His prediction was realized a short time later by the finding 
of the emery variety of corundum, and there subsequently followed 
the conversion of a profitless iron mine into an extensive and profit- 
able emery mine. The finding of chlorite in connection with perido- 
tite rocks has been the starting point for the location of a number of 
large corundum deposits. 
To anyone who wishes to search for corundum it is suggested that 
lie be thoroughly familiar with the mineral itself, as well as with its 
associates, for many instances could be cited where other minerals 
have been mistaken for it. Thus the mineral albite, one of the feld- 
spars, is sometimes very similar in appearance to corundum, and has 
been mistaken for it, but the specific gravity and the hardness should 
at once distinguish it from corundum, albite being much lighter and 
softer. It is w^ell in prospecting for corundum always to have a 
specimen of the pure mineral at hand with which to test the hardness 
of any material that may be supposed to be corundum. In testing the 
hardness of a mineral care should be taken that all decomposed and 
altered material be broken away and that the test be made on the 
pure unaltered material. 
Where it is possible the prospector should visit either a corundum 
mine or a locality where prospecting has been done and corundum 
been found in place, and thus become acquainted with the rocks 
inclosing it and its general occurrence. As has been shown in the pre- 
ceding pages, it is rare that any two localities are exact duplications 
of each other, even when they are close together, yet there are certain 
minerals that are to be found in the same type of rock at nearly 
all of those occurrences, and familiarity with these, even though but 
from one locality, will be of considerable value in the search for new 
localities. 
Where the deposits of corundum are associated with the peridotites 
the mineral will be found chiefly near the contact of the peridotite 
with the gneiss or other country rock, and the deposits within the 
peridotite area will usually be small and in a short distance pinch out. 
Hence in prospecting over a peridotite area a careful, systematic 
search should be made along the line of contact. Corundum may 
