1819.] the Turquoise and the Calaite. 415 



sometimes indurated clay, sometimes porphyry, and sometimes 

 lava. But having shown above that the matrix, when treated 

 by the blow-pipe, becomes attractable by the magnet, an expe- 

 riment which Dr. Macmichael repeated before my eyes, there 

 can be no doubt that it is an argillaceous iron ore. It was 

 respecting this species that M. Agaphi made researches on the 

 spot without being intimidated by the fear of death, or of becom- 

 ing a slave. Naturalists will doubtless concur with me in my 

 desire to erect a monument, though not a very durable one, for 

 such heroic researches, by giving to this species the name of 

 agaphite. The following is the account which he sent to the 

 late M. de Lawadowsky, Minister of Public Instruction, such as 

 it was published by Pallas, and afterwards in our Memoirs, in the 

 place cited above, among the bibliographical notes respecting 

 calaite. 



" On my return from India to Russia by land, I passed 

 through the Khorasau, not far from Pichapour (Nichabour). I 

 was informed, to my great satisfaction, that it was the only part 

 in all Asia which possessed mines of turquoises. Eager to see 

 these mines, I despised the risk of being made a slave, accord- 

 ing to the custom of the country, and I resolved to examine 

 myself the manner of obtaining the turquoise to remove my 

 doubts, and thus to confer a benefit on the scientific world. 



"The following are my observations on these mines. They 

 satisfied myself, and will, perhaps, be agreeable to other natu- 

 ralists. The mines of turquoise occur in mountains, which are 

 not very high, and whose surface is covered with an arable soil 

 mixed with sand, but which, in consequence of the heat of the 

 climate, produces nothing but bent. No certain index of these 

 precious stones occurs; but the inhabitants are led to suspect 

 their existence from the ochre-brown pebbles which are found 

 at the bottom of these mountains, and endeavour to discover 

 them by digging pits of no great depth. - 



" I visited with much attention several mines already disco- 

 vered, and I found that the matrix of the turquoise forms veins, 

 which appear to extend in all directions as the branches of a 

 single trunk, or as the secondary arms of a river; so that, when 

 a small vein is discovered, it is only necessary to pursue it to 

 discover others of more importance. 



" The matrix of the turquoise occurs in horizontal beds, (like 

 that of chrysoprase) which have from 1 line to 10 lines in thick- 

 ness. In these it is disseminated ; so that a piece is very rarely 

 found which is 12 or 14 inches in length and breadth. Among 

 the beds which contain the turquoise, either in veins, or dissemi- 

 nated 'in grains, or reniform, are found likewise beds of the 

 matrix of the same thickness, but without the turquoise. 



" Among these veins are chosen the pieces, which contain 

 xlie turquoises in mass, and very little of the matrix. It is diffi- 

 cult to discover among many pieces a pure turquoise of the size 



