174 PHYSIOGRAPHY. 



grains. Fracture conchoidal in one direction, 

 fine grained in another. 



Lustre intermediate between vitreous and resinous. 

 Colour black, inclining but little to brown. 

 Streak white. Very small fragments are trans- 

 lucent, almost colourless, sometimes a little yel- 

 lowish. 



Hardness equal to that of the yellow variety. 



From the analysis of these different kinds, BERZELIUS 

 obtained the following results : 



Black. Yellow. Dark. 



Oxide of Tantalum 57'00 59-5060-124 51-815. 

 Yttria 20-25 24-9029780 38-515. 



Lime 6-25 3-29 0-500 3-260. 



Oxide of Uranium 0-50 8-236-622 1-111. 



Tungstic Acid with Tin 8-25 pure 1-251-044 2-592. 

 Oxide of Iron 3-50 2-72 1-155 0-555. 



These three kinds have been discovered and described by 

 BERZELIUS in the Afhandllngar i Fysik, &c., Vol. IV. 

 p. 268. By themselves they are all infusible before 

 the blowpipe ; but they decrepitate and acquire a lighter 

 colour. The black Yttro-tantalite froths and melts with 

 soda, but not the others. Borax dissolves them and forms a 

 yellowish glass, which easily loses its transparency. They 

 are not acted upon by acids. 



The different kinds of Yttro-tantalite occur at Ytterby, 

 and in the neighbourhood of Fahlun in Sweden. 



ZEAGONITE. 



GEM. 



Abrazite. Zeagonite. Oismondine. PHILL. p. 11. Gis- 

 mondin. LEONH. S. 645. 



Pyramidal. P = 122 54', 85 2'. Vol. I, Fig. 8. 

 BROOKE. Combination observed, P. P 4- o>v 



