jo Elements of Mineralogy. 



Marbles. 



Opake ftones of any fort, fomething 

 harder than limeftones, more compact, of 

 a clofer grain and fufceptible of a good polim, 

 have been called Marble by ftatuaries, but 

 this name is now appropriated to ftones of 

 the above defcription, of the calcareous genus 

 only- The fpecific gravity of Marbles is from 

 2,7 to 2,8, their texture like that of lime- 

 ftones is either lamellar or granular and their 

 colours various, not only in different mafles, 

 but in one and the fame piece; thefe laft will 

 be mentioned among the compound fpecies : 

 when the different fpecies are in large diftindt 

 maffes they are called Breccias, Marbles of 

 three colours, grey, yellow, and black; which 

 abound in petrifactions, are called luma- 

 chellis ; thofe of four colours, white, grey, 

 yellow and red, are called Brocatellos. I 

 ihall here only mention the purer forts that 

 contain the leaft mixture of foreign genera. 



White Marble, particularly that of Carrara^ 

 is the pureft with which we are acquainted; it 

 is of a granular texture and fparkling in its 

 frafture like fugar ; its fpecific gravity is 

 2,7175, of this fort is the Pietra Elajlica of 

 'Rome. Ferber, Italy, 130. Other white mar- 

 bles are not fo pure, many are of a lamellar 

 texture. 



Black. 



