F. A. Genth’s Contributions to Mineralogy. 199 
ering the bases RO to be combined with alumina in 
1. The formula for the above mineral would nearly re- 
mole: 2k Al+A1,Si,. wal spay 
It may be interesting to state that calculating in Jacobson’s 
pel ape of the Polewskoi staurotide the magnesia as being com- 
bined with alumina, we would obtain from 8°67 to 8°82 per cent 
of aluminate, and the oxygen ratio of the remaining bases R,O, 
is :. SiO, would be as 1°18: 1 and 1°15: 1 or nearly the same as 
t the Canton mineral. ; 
Jacobson’s other analyses, calculated in the same manner, 
give different results, and after deducting the magnesia as alu- 
minate, we get for the bases R,O, and SiO, in the Brittany min- 
eral the ratio 1-23: 1, in that from Airolo near St. Gothardt, 1-48 
and 1-42: 1, and in that from St. Gothardt from 1:88 to 1:62 : 1. 
The difficulties in the analysis of staurotide, especially with 
Tegard to the quantity of silicic acid and the separation of the 
bases RO from those R,O,, and the doubts existing as to the 
State of oxydation of the iron and manganese, render it very de- 
Sirable to have this mineral re-investigated. Not before a series 
the most careful analyses of the different varieties of pure 
? Staurotide have been ma e, can the true constitution of this spe- 
: “les be established. 
12. Chrysolite and minerals resulting from its alteration. 
lite, or especially the 
ie bags latel ived ral specimens from a new locality, 
ae = Webster. Sabie onihty: ‘N. = gas examination of 
th appears to give evidence that chrysol 
ae ee ohio talc slate and many of the serpentines have 
but rall i friable 
y very minute) and very triable, 4 
_ e, of a ae Per “oat ggg 
te, 
