Account of some new Vesuvian Minerals. 253 
2. In a greenish brown compact rock, which at first sight 
resembles petrosilex, but i As, in reality, somewhat similar to 
ed nodules 
id brown c 
3. Ina whitish brown ere ie 5 A the preceding, con- 
taining fine grains of calc 4 
4. An aggregate as to oN 0. 2, into which pyroxene 
enters as a constituen 
All these aggregates are found as nodules in the matters 
ejected by early eruptions. 
The minerals most frequently accompanying this substance 
are fibrous and shining Thompsonite—mica, spinelle, py- 
roxene and spathic carb. lime. 
According to analysis, it is composed of 
Silex 54.16 containing oxygen 27 - - - 9 
Lime = 31.67 rs Soa ee 
Magnesia 8.83 os . o> ae 
Alumine  .50 
Ox. of iron 2.00 
97.16 
Loss 2.84 
100. 
The formula expressing the chemical composition of this 
new Vesuvian mineral is 3CS24+MS°. 
In order to compare the position of the Umboldilite with 
the double silicates of lime and mOGDEEI, which it most 
nearly approaches, their formule are 
Umboldilite 3CS8?2 fae 
Melihite 3CS+ 4MS+f gs $ 
Common pyroxene CS?+ MS? 
Malacoltie + MS? 
Common amphibole CS.3 4+ 2MS? 
Characters See the Umboldilite from other spe- 
ctes to which i t approvimates by chemical or geometgical 
characters. 
The umboldilite a teaagae by its primitive form, the fol- 
lowing: anhydrous sulphate of lime, eryolite, cymophane, 
peridot, stilbite, dipyre, and aniaicee e. 
The chemical and physical characters show a great difference 
between this and the first two on the list: from cymophane 
