Account of some new Vesuvian Minerals. 259 
‘The Davina, according to analysis, has in the 100 parts 
- Silex 42.91 containing oxygen 21.58 7 
Alumine 33.28 6 “6 15.54 5 
Lime 12.02 ~s + MP | 
Tron 01.25 . 
Water 07.43 = = 6.55 S 3 
Loss 03.11 
160. 
The formula should then be CS?4+5AS42aq: i. e. one 
atom of bisilicate of lime, five of silicate of alumin 
of water. The species to which it is nearest allied are ad- 
ded, with their formule, viz... 
Zeolite of Borkhult, =CS?4+3AS. 
Prehnite of Konfolite,=CS?4+2AS. 
CAVOLINITE? 
ystals of Davina to analysis, some of t ; 
-and yielded a different result, having potash as a constituent. 
ist, well known. , 
Specific characters. 
Geometrical characters. 
hedral ; the height of prism less 
prism divides with extreme facility, Sora 
the cleavages are very indistinct, and the mechanical division 
very difficult. 
"Physical characters. It scratches glass. “The gies 
are always opaque and white : the lustre —- or scat 
Longitudinal fracture fibrous, cn gle a - 
fracture rough and unequal. Sp. gr. 2-19. 2 
Chemical characters. When erised and eect 
Nitric, or idio-cloric acid, it is converted into a perleé ee 
without color. Before the blowpipe it fuses easily, wi 
Primitive form is a regular hexa- 
than the breadth. The 
parallel to the axis, but 
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