Dr. Thomson’s Notice of some new Minerals. 193 
The proportion of alumina in chabasite is greater than in 
acadiolite. If this difference be constant acadiolite must be 
considered as a new species. Its constitution, and that of 
chabasite, may be represented by the formulas— 
Acadiolite . . . 2 (AlS%) + Cal S* + 6 Ag. 
Chabasite . . . 3 (Al S?) + Cal S® + 6 Aq. 
9. Prasilite-—To the next mineral species which I shall 
mention [ have given the name of Prasilite, from the green 
colour by which the only specimen which I have seen is cha- 
racterized. It is found in the Kilpatrick hills, and was 
brought to me some years ago by a gentleman while attending 
my class. He had picked up the specimen and brought it 
that I might tell him its name. On looking at and examining 
its hardness and texture, I pronounced it to be sulphate of 
lime tinged by an admixture of epidote; but upon examining 
it chemically, I soon discovered that the opinion formed from 
its external character was erroneous. 
The colour is dark leek-green, and the hardness not more 
than 1; for it does not scratch selenite. It is opake, and has a 
specific gravity of 2°311, which comes near to that of selenite. 
It may be crumbled to powder between the fingers. It is 
composed of fibres very loosely adhering together. "When 
heated to redness it gives out 18 per cent. of water, assumes 
a light yellow colour, and becomes much harder. Being sub- 
jected to analysis, its constituents were found,— 
Wateriy dhs i t,che vy. .eh <9 BOG 
SoRTiGmie stay Vavistl a" soe Tava cere oe 
Magnesia.....--- 15°55 
mee ch.Nevcrere ee t,o 
Peroxide of iron. ... 14°90 
Oxide of manganese .. 1°50 
Mismintss-.ils eae Se he ES 
96°70 
The loss, amounting to 3 per cent., was probably an alkali. 
Prasilite is obviously a triple sesquisilicate. Its constitution 
may be represented by the formula 
8 (Mg S!2) + 4(fS'4) + 3(Al S'2) +18 Aq. 
10. The next mineral which I shall notice is one which 
occurs in the beds of iron ore at Franklin in New Jersey, and 
was first noticed by Messrs. Keating and Vanuxem about the 
year 1822, under the name of Jeffersonite. Keating made 
an analysis of it, the result of which induced me to place it 
among the magnesian minerals, and intimately connected with 
pyroxene and amphibole. But having got a specimen of it 
through the kindness of Dr. Torrey of New York, I subjected 
Phil. Mag. 8. 3, Vol. 22. No. 144. March 1843. O 
