Iron. 273 



rites,&c.and does not give fire with fteel, unlefe 

 thefe foreign fubftances be ftruck. Its fpe- 

 cific gravity is from 3,6 to 3,895, or 4,00 

 it feebly effervefces with acids, particularly 

 when pounded and heated, affords from 20 to 

 27 per cent of fixed air. It is fcarce ever 

 magnetic before calcination, but if heated, 

 it decrepitates, grows black, becomes mag- 

 netic, and lofes from 15 to 40 per cent of 

 its weight. 



9. 100 Parts of this ore from Eifendrtz 

 in Steria, afford according to Mr. Bergman, 

 38 of the brown calx of iron, 24 of the white 

 calx of manganefe, and 38 of mild calcareous 

 Earth. Another fort from Weft Silvretberg 

 contains 22 of the brown calx of iron, 28 

 of the white calx of manganefe, and 50 of 

 mild calcareous Earth. What quantity of 

 iron and manganefe in a reguline ftate, thefe 

 quantities of each calx would produce, may 

 be feen by the table inferted at the end of 

 this treatife ; the aerial acid is united not only 

 to the Earth, but alfo to the metallic calces, 

 as appears by its proportion. Many other 

 ores are poorer, and fome to fuch a degree as 

 not to deferve the name of an ore. It is fre- 

 quently mixed not only with quartz and py- 

 rites, as already mentioned, but alfo with 

 fhoerl, zeolyte, mica or afbeftos. 



T When 



