416 Dr. Gottkelf Fischer's Essay on [Deo. 



of a pea. Those of the size of a nut are very rare, and very much 

 valued, as the commerce of turquoises with the Afghans, the 

 Persians, and other Asiatic nations, is very great." 



The finest agaphite, or calaite, in layers which I have hitherto 

 seen is in the collection of M. Weyer, jeweller at Moscow. It 

 is of the finest colour, cut in the form of a heart, and is two 

 inches five lines in length, and two inches nine lines in breadth 

 at the broadest part. It is accompanied by the matrix, which 

 has received the same form, to serve as a support to the stone, 

 which of itself is too thin to be cut into a table shape. What 

 renders this stone more remarkable is, that it served, according 

 to report, as an amulet, or talisman, to Nadir Shah, containing a 

 verse of the Koran very well engraved in gilt letters. It was 

 purchased at Meched, and M. Weyer offers it for sale at the 

 price of 5000 roubles. 



3. Johnite. 



Quartzy turquoise, vitreous, or scaly. Mem. de la Soc. des 

 Nat.i. 149. 



It has a light-blue colour, which passes into green. It occurs 

 in very thin layers, in a black siliceous slate. It is harder than 

 the two other species, scratches glass strongly ; but does not 

 give sparks with steel. The fracture of it is scaly. 



This species, as I mentioned before, is more rare than the 

 others. I am acquainted only with one specimen in the collec- 

 tion of M. Wagner. It certainly exists more frequently in 

 nature, but is seldom met with in commerce, because it is not fit 

 to be polished. 



Its specific gravity and chemical composition are unknown ; 

 but it is probable that it contains some silica, in consequence of 

 the siliceous matrix with which it is accompanied. We have 

 not been able to discover any thing respecting its position. 



I have given to this species the name of Johnite, in honour of 

 Prof. John, of Berlin, who, by his chemical researches, daily 

 gains more and more of the esteem of men of science. 



lines. 



Calaite is employed as an ornament in diadems, bracelets, 

 rings, with or without brilliants ; or, especially among the 

 Persians, to adorn the handles of knives, sabres, 8cc. or to con- 

 struct talismans, as I have mentioned above. 



Chap. II. — Of the Odontolite, or Occidental Turquoise. 



The article respecting the odontolite turquoise requires to be 

 treated as an object of zoognosy. The following are the prin- 

 cipal questions which require to be answered : 



1 . What are the parts of the skeleton hitherto found converted 

 into turquoise? 



2. To what animal do they belong ? 



3. Where do the principal depots occur ? 



