182 TRANSACTIONS OF THE [APR. 16, 
Our analyses result as follows: 
ile 2. Average. 
Ignition loss, 4.64 (4.64) 4.64 
SiO, 38.68 38.80 38.74 
Fe,O, 6.85 (6.85) 6.85 
Al, 0, 6.45 6.71 6.58 
Mn,O, 15.80 ea 0 15.95 
CaO 22.68 21.92 22.30 
MgO 5.43 5.60 5.52 
100.53 100.63 100.58 
The molecular ratios, calculated from the average of these 
analyses, are: 
SiO, .643 .643 3.09 
Fe,0, 043 ) 
A1,0,- as. 0645.7 208.1 (2100 
Mn,O, 101) 
CaO .398) we Sw 
MgO 138 ) 536 9.57 
HO .258 .258 1.24 
showing ratio, of SiO, aR 5032) K0: H, O=632e5=2.5. hs 
does not suggest any ver y. probable formula, a ane to be ex- 
pected from the way in which the mineral was produced. 
Mr. Heinrich Ries, Fellow in Mineralogy at Columbia College, 
who made optical examinations of this mineral and of the asso- 
ciated biotite, writes as follows: ‘The new mineral is very 
feebly doubly refracting, and shows apparently no pleochroism 
in a section at right angles to the base. It is more strongly 
biaxial than the biotite from which it has altered, but it is so 
feebly refractive that only poor images could be obtained. 
With the gypsum plate, showing red of the first order, it acts 
like an isotropic mineral, so that the character of the double 
refraction could not be determined. The biotite with it shows 
a slight divergence of the optic axis probably not more than 5°. 
A flake was struck with a sharp point to obtain the percussion 
figure, and the leading ray of the latter was parallel to a line 
joining the loci of the optic axes, proving it to be a mica of the 
same order as biotite.” A very dark red mica with brilliant 
lustre, from the same mine, and associated with similar minerals, 
was also examined optically, and proved to be a fresh, unaltered 
biotite. Chemical examination showed the presence of potash 
in considerable proportion in this unaltered biotite, while it is 
found in slight amount in the biotite occurring with the cas- 
