PROCEEDINGS OF THE CANADIAN INSTITUTE. jr 



Corundum in Ontario. By Archibald Blue, Ksg. 



(.Read loth December, 1898.) 



Just one hundred years ago, in a paper read before the Royal Society of 

 London and published in its Transactions, Rt. Hon. Charles Greville established 

 and named nhe mineral species Corundum, the crystalline oxide of aluminium; 

 and we have it on the authority of Professor Judd that in an appendix to Greville's 

 paper the Cpunt de Bournon correctly defined the crystallographic characters of 

 the species. The names of its gem-varieties, sapphire and ruby, had been in use 

 from a much earlier time:<i> and the name corivindum, or corrivcndum, had been 

 given to it by Woodward, in a vaguer way, as early as 1714. 



In the western part of Asia Minor, and in some islands of the Grecian Archi- 

 pelago, the crystalline limestone which is interbedded with the schists and gneisses 

 carries a blue corundum mixed with magnetite, which is the emery of commerce. 

 The corundum occurs in smaller quantities as a constituent of granite and gneiss 

 in Silesia, Auvergne and elsewhere in Europe; in a compact felspar rock in Pied- 

 mcmt; in dolomite with tourmaline at St. Gothard; in crystalline limestone, along 

 with numerous other minerals, in Orange and Westchester counties. New York, 

 and Sussex county. New Jersey, and at various localities in Connecticut, Massa- 

 chusetts and Pennsylvania. It is said by Dana to be common at many points along 

 a belt extending from Virginia across western North Carolina and Georgia to 

 Dudleyvilie, Alabama. 



In Burma, which became a British Province in 1886, ruby mines have been 

 worked for a very long period. There the country-rock is chiefly gneiss, with 

 bands of crystalline limestone of varying thickness and many miles in length. Most 

 of the mining has been carried on in the hill-wash and alluvium carried down from 

 the decomposed summits of hills and mountain ranges; and it has been observed 

 that where the sands and gravels are mixed with a dark brownish earthy clay, 

 which is a product of the decomposed crystalline limestone, they are richer in 

 such gems as ruby and spinel. The explorations of Barrington Brown appear, 

 indeed, to have satisfactorily established that in Burma the only rock in which 

 rubies are found in place is crystalline limestone. " It is of the usual composition 

 and character of ordinary crystalline limestones," says Mr. Brown, "being made 

 up of finely crystalline or granular limestone in layers, together with irregularly 

 shaped bands of very coarsely crystalline limestone of white and bluish colors, 

 which are interfoliated with the gneissic rocks." Where a quarry has been worked, 

 near Mogok, the matrix of the ruby is a coarsely crystalline, semi-opaque lime- 

 stone of about twenty feet in width. The rubies are found over a space of six feet 

 in width, extending almost vertically from the bottom of the quarry to the surface 

 of the ground, and along the centre-line, where the rubies are most numerous, are 

 small developments of a grayish diaspore enclosing small crystals of iron pyrites. 

 As to the limestone itself, whether occurring as disseminated crystals through the 

 gneiss or as great interfoliated masses, it is the opinion of Professor Judd that it 

 has been neither organic nor due to direct chemical precipitation in its origin, l)Ut 



(i) In the Burma Corundum every shade of colour, from white to the highly prized deep crimson or 

 pigeon's blood, is found, and they are named according to colours instead of composition or system of crys- 

 talization,— the red variety as oriental ruby, the blue as oriental sapphire, the yellow as oriental topaz, the 

 purple as oriental amethyst, and the green as oriental emerald. ^ 



