414 Dr. Gotthelf Fischer's Essay on [Dec. 



posed by carbonate cf ammonia, three grains of pure alumina 

 were obtained. 



n. The liquid / freed from alumina and iron was saturated with 

 nitric acid, and mixed with a solution of prussiate of potash. 

 By this means |th of a grain of oxide of copper was obtained. 

 Thus 100 parts of the calaite subjected to experiment furnished 



Alumina of c 70*00"? ^^.q 



m 3-00 5 



Oxide of copper of g 4257 A .r 



n 0-255 4i> 



Water 18-0 



Oxide of iron of/ 1-00 ? d . n 



I 3-005 40 



Lead and loss 0-5 



100-0 

 Position. 



Calaite occurs in alluvial grounds, and as far as we know at 

 present, only in the neighbourhood of Nichabour, in the Khora- 

 san, in Persia. It ought to be of the old rock ; for we find it 

 very seldom in commerce, and I have only seen the specimens 

 of it which I have mentioned above. It is probable that these 

 kidney-shaped pieces occur in beds of a brownish clay. The 

 rounded or rolled pieces necessarily belong to this species. 



2. Agaphite. 



Conchoidal calaite, conchoidal turquoise. Mem. de la Soc. 

 Imper. des Natur. i. 149. 



The agaphite varies most in colour. It occurs of the palest 

 and of the deepest sky blue. But its external figure is constant, 

 as it occurs always in layers in an argillaceous oxide of iron, 

 more or less hard. Its layers vary in thickness from a line and 

 less to five lines. It is opaque ; but the darkest coloured speci- 

 mens, which are also the smallest, are translucent on the edges. 

 Sp. gr. 3-25, Fischer ; 3-00, John. 



Chemical Characters. 



We have not yet obtained an exact chemical analysis of this 

 species ; but we" have no reason to doubt the assertion of Dr. 

 Macmichael, who, just after his arrival from Sweden, assured us 

 that the celebrated Gahn had undertaken an analysis of the tur- 

 qiioise, according to whom it is coloured by arseniate of iron. 

 This analysis can only be applied to the agaphite. 



Position. 



It is found in beds accompanied by a very indurated argilla- 

 ceous ironstone. The matrix has been sometimes called tile-ore, 



