412 Dr. Gotthelf Fischers Essay on [Dec. 



Physical Characters. 



It is moderately heavy. The specific gravity varies according 

 to the different varieties : 



Grass-green calaite 2-7568 Pansner 



Apple-green calaite 2* 6296 Ditto 



Mamellated ditto 2*860 Fischer 



3-000 John 



Slaty ditto 3-250 Fischer 



None of the varieties of calaite appeals to acquire any electri- 

 city by friction. 



Chemical Characters. 



AH the varieties of calaite remain unaltered though plunged 

 into muriatic acid.* 



Muriate, or scoriacious copper, which approaches much to 

 some varieties of calaite, acquires, when plunged into the same 

 acid, a more beautiful colour, and becomes transparent like the 

 emerald ; but when dried, becomes covered with a white coat. 



This examination of the external characters of several calaites 

 shows clearly that there are three distinct species differing in 

 their fracture, colour, specific gravity, constituents, and position. 



1. Calaite, properly so called. 



Calaite, Fischer, Mem. des Nat. i. p. 149. Onomasticon 

 (1815) p. 8. familia Argillas. 



Turcosa, Fischer, Onomast. (1811) p. 53, after the wavellite. 

 (Syn. Turchesia ; Turchin.) 



Tiirkis, Ullmann, Mineral, einf. Fossilien, p. 76, n. 103. 



Dichter Hydrargillite, Haussmann Handb. der Mineralogie, 

 p. 444, c. 



This species is almost always of the fine blue, which I have 

 called calaite blue ; it occurs in reniform and botryoidal pieces ; 

 it is opaque, and not even translucent on the edges. Sp. gr. 

 2-860, Fischer. 



Chemical Characters. 



Calaite is a clay, coloured by oxide of copper. Professor John 

 made an interesting analysis of this variety for the Society of 

 Naturalists. The museum of Moscow furnished him with the 

 necessary specimens, with the permission of Chevalier Paul de 

 Demidofr, as the collection was in possession of several. As it 

 is interesting to know the process of M. John, I shall transcribe 

 his account of it such as he deposited it in the archives of our 

 Society. 



* The French jewellers consider it as a principle, that the true turquoise should 

 effervesce in sulphuric acid. This is a proof that they think only of the French 

 turquoise, or turquoise odontolite, the true stone, or calaite, not yielding to Ibe 

 s(-rons;est acids. 



