410 Dr. G oft helf Fischers Essay on [Dec. 



orvctognostic system, and to add to the notions which we have 

 respecting the turquoise odontolite. some new discoveries, at the 

 same time that I exclude it, as ought to be done, from the num- 

 ber of stony bodies. 



Chap. I. — Of the Calaite. 



Description of the external Characters of the Calaite. 



Calais, Plin. Baptoea in Russian, birousa in Persian, turquoise 

 vulgarly. 



Colour. 



Calaite is blue, intermediate between sky-blue and pale verde- 

 gris green ; that is to say, of a peculiar blue, which must be 

 called calaite, or turquoise blue. It may be obtained by mixing- 

 two parts of mountain blue with one part of mountain green. 



This blue passes on the one side through smalt blue to the 

 finest sky blue ; on the other side through pistachio-green to 

 apple-green, which does not yield in any thing to the most 

 beautiful chrysoprase. 



Yellowish-green and celadon-green are the colours of pieces 

 altered by the atmosphere without, being decomposed. Botry- 

 oidal portions are usually observed on the surface, sometimes 

 surrounded by a layer of yellow matter down to their roots, 

 giving to pieces thus cut the aspect of annular. 



External Shape. 



It occurs massive, in layers, and disseminated. 



a. In reniform masses which, at the surface, are mamelated 

 and botryoidal ; from the size of a nut to that of a goose egg. 

 The largest piece that I have seen is in the museum of the 

 Imperial University of Moscow, coming from the rich donation 

 of his Excellency Councillor of State, the Chevalier Paul de 

 DemidofT. This piece is 3i inches long, 1 inch 8 lines in 

 breadth, and 1 inch 2 lines in thickness in some places.* Jt 

 weighs four ounces five drachms. His Excellency Dr. Crichton, 

 Councillor of State at Petersburgh, possesses a piece which is 

 not much smaller. This gentleman, equally celebrated and vene- 

 rable for his medical skill and his goodness of heart, has formed 

 a collection of minerals which may be called the coquetry of 

 science. The rarest objects, the most perfect and most varied 

 crystallizations, form the principal object of this collection. The 

 third piece in point of grandeur belongs to M. Wenck. It 

 weighs 17-i- solotniks, or 1035 gr. 



b. In rounded pieces ; very rarely ; I have seen in the posses- 

 sion of M. Wagner, member of our Society, a single piece, 

 which seems to have been rounded by the action of water. I 



* This piece, like all those which pass legitimately in commerce, has the Persian 

 mark of its origin and authenticity. 



