852 General Notes. 
This mineral differs from biotite in the possession of water 
and a smaller percentage of potassium. As Hoppe-Seyler* 
dioxide and water it loses potassium and gains water, Knop 
thinks that this mineral, which he calls psewdobiotite, may have 
are SiO, : R,O,: Ro=2: 1: 1.5, corresponding to the formula 
Ry’R,'Si;0)3. Professor A. H. Chester? has recently we 
SiO, ALO Cr,O, FeO, CaO MgO K,O NaO ‘ 
45-49 31.08 3.09 trace osr 3.36 9.76 0.90 § i 
A pink celestite from Landsville, Oneida County, N. Y., yiel 
ström reports the existence of a manganiferous vesuvianite WÈ 
4.72 per cent. of MnO. 
Crystallographic News.—Chas. O. Trechman$ describes ory* 
tals of barite from Addiewell in Midlothian, England. 
however, that the structure of the mineral corresponds pi 
orthorhombic symmetry, with the axis of least elasticity 1 
to one of the cubic faces Mr. H. A. Miers? mentions © 
clase twins fromthe augite andesite of Kilimanjaro, 1m bles 
composition face (as well as the twinning plane) is the $ Pa 
acoid. The crystals are bounded by the planes oP, eT 
and oP. | a ah 
* Zeits. d. dents. G oe 
* Zeits. f. Krys oe Gh 3 Amer. Jour. Sci., April, ae : 
i alee - 1. Soc. Fr. d. Min., ix. p. 22. s Min. Mag., Dec. 1986, Oe 
+ £ Kryst., xii. p. 552. 7 Min: Mag., July» 1886, P- © : 
