Salts. 185 



in the mineral lakes of Tufcany, 16 Roz. 

 362. alfo germinating on the furface of free 

 ftone or fhiftus in coal mines, or on lavas 

 near volcanos, and on feveral rocks in the 

 Arch'jpelago, and in feveral parts of Hungary, 

 Bohemia, and Swifferland, though feldom 

 pure ; but far the greater part of it is facti- 

 tious, being extracted from various ores, the 

 principal of which are the following : 



SPECIES VII. 

 <A luminous Ores. 



i ft - Sulphurated Clay. This conftitutes the 

 pureft of all aluminous ores, namely, that 

 of La Tolfa near Cwita Vechia-\ it is white, 

 compact, and of the hardnefs of indurated 

 clay ; hence called Pe.tr a ^llummaris^ yet 

 mealy and taftelefs. Mr. Monnet firft dif- 

 covered the real nature of this ore. Accord- 

 ing to him 100 parts of it contain upwards 

 of 40 of fulphur, and 50 of clay, befides a 

 fmall quantity of fixed vegetable alkali, and 

 a very minute portion of iron. 13 Roz. 

 Supplem. p. 338. With this Mr. Bergmans 

 analyfis nearly agrees j 100 parts of this ore 

 containing, according to him, 43 of fulphur, 

 35 of argill, and 22 of filex. 3 Berg. 271. 

 He alfo found the vegetable alkali and iron, 

 but probably he did not feparate them, but 



reckoned 



