364 Count DE Bournon on BardigUone, 



specimen of it that exhibits an interesting fact. Its surface shews the 

 union of an immense number of small rectangular prisms, all, or 

 nearly all, having their planes in a parallel direction ; but a very great 

 number of them are very distinct in all the extent of their square 

 surface. This texture appears to have been occasioned by a very 

 slight alteration. The matrix of this bardiglione is an indeterminate 

 massive quartz, to which there adheres a fragment of foliated mica- 

 ceous rock, mingled with galena and some iron pyrites. It came 

 from the lead-mine of Pesai, near Mont Blanc 



4. With small lamina intersecting each other in different directions. 

 The bardiglione of Vulpino frequently presents us with this 

 variety, which sometimes has a very deep bluish colour, and is fre- 

 quently mixed with a few particles of quartz. We are indebted to 

 M. Fleuriau de Bellevue for a knowledge of the different varieties 

 of the bardiglione at Vulpino. It was he who found that this sub- 

 stance, which takes a very fine polish, and is employed by the sta- 

 tuaries of Bergamo and Milan for making slabs, chimney-pieces, &c. 

 differed essentially both from carbonate of lime and gypsum. The first 

 analysis of this substance having shewn it to contain sulphate of lime 

 and quartz, the latter in the proportion of 0.8, it was called quartzi- 

 ferous sulphate of lime ; till a second analysis by Vauquelin ascer- 

 tained its real nature. The interposition of quartz, and the interrup- 

 tion of contiguity occasioned by this interposition, diminishes its 

 specific gravity, which was found to be 28.78 by the Abbe Haiiy, 

 who some time after discovered that it belonged to the bardiglione. 

 The quartz interposed in this substance may sometimes be perceived 

 by a good lens. 



Sometimes too this variety of bardiglione, and more particularly 

 the following, in the granular state, includes particles of carbonate of 

 lime, but always in very small quantity. 



