258 Curjoty View of fome 6f thd 



. , Lelievre has defcribcd a mine of uranite difcovered in thC 

 department of Saone and Loire. 



The pt-rljlein of Werner (pearl-ftone) is found in alternate 

 llrata with argillaceous porphyry, reding on trapp, on the 

 road between Tokai and Kereftour. This is what Fichtel 

 calls 'Volca7nc zeolite. This fubftance is of a tarnifhed blue 

 colour, has a refmous fra6lure and a pearly appearance. 

 The interior of it is formed by the union of feveral fmall 

 grains of black obfidian ftonc inclining to blue, each fur- 

 rounded by a pearly pellicle of that fubftance. It is tranf- 

 lucid, fragile, and pretty light. Its gravity, according to 

 JFIaiiy, is 2*540. 



Launoi has brought from Carboneira, in Spain, a fub- 

 ftance analogous to the above, which, in imitation of the 

 Germans, he calls luchs-faphir. 



Werner is of opinion that this ftone is not volcanic; he 

 places it between the quartz and the hornftein : the horn-- 

 ftein is a kind of fubftance whith the French, in imitatiort 

 of the Swedes, call petro-Jile.v. 



Humboldt is of opinion that the pumice ftone found on 

 tiie peak of Teneriffe is only obfidian ftone decompofed by 

 iire. According to this naturalift, its. origin cannot be 

 gfcribed to fcld-fpar. He collected a great many fragments,, 

 which were half obfidian and half fibCous pumice ftone : 

 fhey were of a black olive colour. He faw fpecimcns of the 

 like kind in the cabinets of Madrid. 



Fortis fays that the Venetian (liips bring from the ifland 

 of Candia, as ballaft, a kind of ftones among which are 

 obferved large blocks of black glafs, or obfidian, exceedingly 

 pure, without any mixture of foreign bodies, which are vi- 

 fibly changed into white pumice ftone by a gradual tranfi- 

 tion, fo that there are fome fragments part of which is ob- 

 fidian and part pumice ftone. 



The fame thing is obferved in the pure obfidian of Liparl, 

 and the ifland of Procida near Naples. 



Kiaproth has analyfed a pumice ftonc, which gave : 



Silex - - - 77-50 



Alumine - - - 17*50 



O.vydofiron •• ~ 0X75 



O^yd 



