Mineralogy and Geology. 423 
Clean scales of the mineral were selected with great care by Mr. 
Silica, . 35°74 containing oxygen 18°56 ratios —6- 
Alumina, : 16-4 : Yt 
Protoxyd of iron, . 10-02 2:28 , 
Magnesia, .  . 27-44 10-62 j 4 
mer.” . 10-30 9°15 3 
99-92 
Which gives approximately the following formula,* 
; 2X1 Si+4Mg3 Si-+-oH 
which is the formula given by von Kobell for Pyrosclerite. 
_ Vermiculite therefore does not approach Pyrophyllite, which, accord- 
ing to the analysis of Hermann, gives the formula, | 
Mg3s Si2+-9A1 Si2--oH 
Mr. Crossley has devoted much time and attention to this analysis, and 
Tam satisfied that it has been correctly made. The only subject for 
farther research is the cause of the very remarkable exfoliation of this 
mineral when exposed to heat. I ascertained the temperature at whic 
the exfoliation takes place by heating the mineral on paper and on lead. 
It fully exfoliates below the fusing point of sheet lead, but not ona 
paper card, until it takes fire. 
- 2. On the Blowpipe characters of the Mineral from the Azores iden- 
tified with Pyrrhite by J. E. Teschemacher ; by A. A. Haves, (com- 
municated.)—I received enough of the Pyrrhite from Mr. Tesehemacher 
for the following trials. It proves to be a (columbate) niobate of zir- 
_conia, colored apparently by oxyds of iron, uranium and manganese, 
The following are its characters in the blowpipe flame. On the first 
impulse of heat, the assay becomes darker colored, its fine red color 
returning as the mineral cools; and this character may be observed, 
even after it has been highly heated fora longtime. At the melting 
point of cast iron in the reducing flame, it becomes permanently darker 
but on cooling, opa : | 
When by continued reduction, the soda is partly evaporated, a gray 
Considering #1 and Si as replacing one another, the analysis gives very exactly 
the formula 4Mg° (Si, 41)2-+91.—J. D. D. 
