950 The American Naturalist. [ November, 
The siliceous matter is partly serpentine and partly a silicate, insolu- 
ble in acid, possibly an impure bronzite. The alloy has a composition 
corresponding to Fe, Ni, Chromite, magnetite and troilite are also 
present in the pebbles, the first two as granules in the silicates. The 
alloy is gray, malleable and sectile, and has a hardness of 5. Its ori- 
gin is probably terrestrial. 
Crystallography.—On crystals of vesuvianite from the blocks of 
onte Somma, Boecker’ finds seven new forms and recognizes a tabu- 
lar type hitherto undescribed. The new forms detected are ¿Pæ , $P, 
$P, &P, P5, tP}, and YPY. He describes also transparent green 
crystals of the same substance implanted in granular yellowish-green 
vesuvianite from Lermatt. 
On topaz from near Miass in the Ilmen Mountains, S. Urals, 
Souheur™ reports a large number of new planes in the prismatic and 
the pyramidal zones, and that between Poo and 3P. The crystals are 
from Redikorzew’s topaz mine, where they are associated with ilmeno- 
rutile, black tourmaline, and muscovite on an amazonite-bearing 
granite. 
The plane Pž has been discovered by Pelikan” in sulphur crystals, 
implanted on antimonite from Allchar, Macedonia. Measurements of 
cleavage pieces of meteoric iron incline Linck" to the belief that the 
twinning of the iron is parallel to the plane 202. 
Mineralogical Notes.—Another calculation of the formula of — 
tourmaline from published analyses leads to the suggestion by Kenn- 
gott that the various members of the tourmaline group are isomor- 
phous mixtures of the compounds 3R,O. SiO, + 5 (R,O,. SiO,) and . 
2 (8RO. SiO,) +.R,0,. SiO, The red tourmaline from Rumford, 
Me., may be regarded as the first end member of the series. The | 
end member is not yet known. 
New analyses of pseudobrookite from the Siebenbürgen yield no 
magnesia. Crystals from this locality, like those from Norway, thus 
consist simply of iron and titanium oxides. They are tabular with | 
co Pas, æ PX, œ P3, œ P, PZ, }PHX and łP, of which the latter is 
Zeits. f. Kryst., xx, p. 225. 
*Zeits. f. Kryst., xx, 1892, p. 282. 
“Min. u. Petrog., Mitth., xii, p. 344. 
"Zeits. f. Kryst., xx, p. 209. 
Neues. Jahrb. f. Min., etc., 1892, ii, p. 44. 
Traube. Zeits. f. Kryst., xx, 1892, p. 327. 
. 
