230 Mineralogical Notices. 
trary to the investigationsof Rose. In an analysis of Samars- 
kite he obtained 
Niobie acid ae ilmenic 5636, U 16°63, Mg 0°50, Mn 1-20, Fe 8°87, ¥ 13°29, 
Ce, La 2:35= 
aeiing 6 teh it is a niobate of protoxyd bases. Color of 
specimen black, with partly a grayish-brown crust. 5°64. 
ie Aischynite ; by R. Hermann, (J. f. pr. Chem. 1, 193.)— 
Hermann has reanalyzed HEschynite and found it to consist of 
Niobic acid, 33°20, titanic acid 25-90, Ge 22°20, Ce 5:12, La 6-22, ¥ 1:28, Fe 5-45, 
H 120100557. 
iy ged and Polymignite, (Hermann, J. f. pr. 1 
Chem., |, 181.)—The angles of polycrase are as fol- 
lows, Ldsidiig to Scheerer and Hausmann’s cal- e\ 
culations: octahedron P, 152° 0’, 90° 2’, 96° 41’; 
vertical prism (p) 140°; brachydiagonal prism (h) 
56° 0’. Hermann observes that if the crystals be 
viewed in a different position, the angles approach 
those of columbite, in which P=150° 17’, 86° 52’, 
100° 49’; brachydiagonal aba (corresponding to 
vertical above) 123° 50’ to 125° 20’; macrodiagonal 
ee | ( RA Sate to brachydiagonal above) 139° 
6’. hot composition is widely different 
from Rigs of columbite, the two minerals are ap- 
proximately isomorphous 
Polymignite is related crystallographically in the same man- 
ner to columbite. «The three prisms of 70° 50’, 109° 10’ and 
140° 51’ in Polymignite, correspond to three prisms 70° 50’, 
109° 35’, 141° 8’, in columbite. To perceive the relations be- 
tween the crystals of the two minerals, the vertical prisms of 
polymignite, as the mineral is usually drawn, should be compared 
with a series of horizontal prisms in colu mbite 
ermann also remarks that Brookite approaches columbite in 
its angles. 
Hermann adopts the view that tantalic and the related acids 
contain 2 of oxygen like titanic acid ; and he concludes also 
toxyds. engite he makes a titanate of pie a of i and 
uranium, cerium ; yttroilmenite an ilmenate and titanate of pro- 
toxyds of yttrium, iron and urahium ; columbite a niobate, pelo- 
pate or ilmenate of protoxyds of iron and manganese (3 of f acid 
to 2 of base.) He also concludes that Wolframic acid has the 
formula W and not W, on the ground that Wolfram (R W) is 
isomorphous with columbite. [‘This last case of isomorphism ap- 
