1 62 
Description and Analysis of Sordawalite. 
tuffa in this respect* that, in the one, the Roman, leucites more 
or less decomposed, occur, but are wanting in the other; while, 
m the Neapolitan tuffa, we can generally observe that the sub- 
stance of felspar lias contributed materially to its formation. 
Where volcanic tuffa occurs along with the more general tertia- 
ry formations, it is always newer than these: Of this we can 
convince ourselves in a most satisfactory manner in the vicinity 
of Rome, where we observe the sand of Monte Mario filled 
with sear-shells, rise from under volcanic tuffa near to the Vati- 
can. 
At the conclusion of the memoir, our author remarks, 1 st, 
That the principal chains of the Appennines contain no true vol- 
canic rocks , nor rocks of the trap formation . 2d, That the 
true volcanic formations are principally confined to the south- 
east side of Italy ; that the greatest extent of these occurs in 
the line of the older rocks, and that only a portion of these, 
such as Vesuvius , the extinct volcanoes of Nemi and Albano , as 
also the remarkable stream of lava of Bor ghetto, approach the 
boundary of the alpine limestone. 
Art. XVI . — Description and Analysis of Sordawalite , a new 
Mineral from Finland , by M. G Nordenskiold, Esq. 
.A. black mineral, somewhat like coal in appearance, occurs in 
the rock on which the church is built, near to the town of Sor- 
dawala. From its resembling the black garnet of Swaphawara, 
in Lapland, analysed by Hisinger, it was regarded as massive 
Melanite. The following analysis, which I made of it, proves 
that it is a distinct and new mineral. Its external characters 
are as follows : 
It occurs massive, and without any traces of cleavage. The 
colour is greenish, or greyish-black. It is as hard as glass. It 
occurs in a thin bed, and breaks readily in a direction at right 
angles to the direction of the bed. The fracture is conchoidal ; 
and the lustre vitreous, inclining to semi-metallic. Opaque. 
Brittle. Specific gravity 2.530. 
N. B It becomes reddish on long exposure to the atmosphere. 
It is found in a bed, from half an inch to an inch in thickness, 
