PRECIOUS STONES 327 



westward to a portion of that state not covered by the earher, 

 and formed there what he terms the Wisconsin boundary, [il- 

 though its source was far east of the earUer drift, and it forms 

 the main de{)osits of the eastern states. 



Professor Blatchley's Ust comprises eight cHamonds that 

 he himself has seen, and seven more of which he has credible 

 information. Tlie earliest published mention of the occur- 

 rence of diamonds in Indiana was made by the late Prof. E. 

 T. Cox, state geologist, in his annual report for 1878, page 

 116, although the well known artist Mr. Daniel Beard, of New 

 York, owns a fine diamond of about 2 carats found in Indiana 

 before that year. Professor Cox mentions several diamonds, 

 of which this may be one, as found in the drift of Brown and 

 Morgan counties, and refers to them with interest because of 

 their evident transportation from a far northern source. Of 

 the eight stones seen by Professor Blatchley, four are from 

 the newer and four from the older drift, or at least from the 

 area covered by it south of the margin of the newer. 



The sapphire, ruby, oriental topaz, oriental amethyst, and 

 oriental emerald are names given respectively to the transpar- 

 ent blue, red, yellow, purple, and green varieties of corundum, 

 which is nearly pure alumina, A2IO3. The colors of these min- 

 erals are ascribed to the presence of minute quantities of metal- 

 Uc oxides. Their specific gravity ranges from 3.97 to 4.05, 

 and their hardness is 9. Rubies are found in Burma, Ceylon, 

 and Siam. Sapphire also occurs in these countries, as well as 

 at the Simla pass in the Himalayas and in Austraha. 



The great hardness of corundum gives it a special value 

 for polishing purposes. Although corundum is found in the 

 crystalline rocks along the Appalachian mountains from Mass- 

 achusetts to northern Georgia, few gems of any special value 

 liave been found, except in the Cowee valley in North Caro- 

 lina, where true rubies are obtained to some extent, although 

 mining has ceased for a few years past. Other deposits in 

 which these gems are found exist in Montana. Sapphires of 

 the finest quality are now mined in Yogo gulch, and others 

 of much beauty are found at other points in the same state. 



Until within a few years, these gems had been found only 

 occasionally in the United States — nearly all of them in North 



