44 Elements of Mineralogy, 



portion of mild calcareous Earth, which alfa 

 varies, from 50 to 70 or 8^ per cent, when 

 lefs, it ihould be reckoned among the (iliceous 

 fand-ftones. 



It frequently contains alfo a fmall propor- 

 tion of argill, and a ftill fmall er of iron. Its 

 furface is generally rough ; its texture moftly 

 granular, but fometimes fcaly : it does not 

 ftrike fire with tteel ; it is fometimes ufed as 

 a limeftone; it hardens by expofure to the 

 air ; it is frequently fprinkled over with 

 mica, but not in fuch proportion as to alter 

 its genus or fpecies. The fand-ftone of St. 

 Helena^ which is very brittle, and burns to 

 lirne, is of this fpecies, 



SPECIES IX. 



Mild Calcareous Earth mixed <wltb Petrol in 

 Jmall Proportion. 



Sivine-ftonc, Pierre Puante, Stinkfteine^ Lapis 

 Suillus, Or [ten of the Swedes. 



The colour of this ftone is either white, 

 grey, yellowifh, brown, or black, with glit- 

 tering particles -, its texture granular, fcaly, 

 or lamellar ; its form either round or prif- 

 inatic, and polygon or amorphous; its grain 

 compact and equable, or looie and open ; its 

 fpecific gravity confequently from two to. 



three : 



