1022 General Notes. 
trachyte and augite-trachyte glasses, which present no features 
different from those observed in the lavas of other craters in this 
region.—Mr. E. O. Hovey! reports the discovery of a cordierite 
gneiss at Guilford, sixteen miles east of New Haven, Conn. The 
cordierite has a deep blue color in the hand specimen, but under the 
microscope is colorless and very fresh. It contains as inclusions 
only sillimanite needles.—Lacroix and Baret? mention a pyroxenite 
om near Saint Nazaire, Loire-Inférieure, France, that is com- 
posed essentially of a granular mixture of augite, scapolite and 
sphene.—The microscopical examination and the determination of 
some of the physical constants of several sandstones, a marble and 
a tufa from California, have been made by Prof. A. W. Jackson, of 
the University of California. 
New Mrnerats— HouMANNITE AND AMARANTITE.—In a 
mass of copiapite from near Caracoles, in Chili, Frenzel* has dis- 
covered two new iron sulphates. One has been called hohmannite 
after its discoverer. This is an opaque chestnut-brown fibrous 
mineral, with a vitreous lustre. Its hardness is 3; specific gravity, 
2.24, and its streak a yellow ochre color. Its composition may 
represented by Fe (FeO) (SO,), + 7H,O. It is insoluble in water, 
readily undergoes alteration, and loses 7.63 per cent. of water when 
placed in a dessicator over calcium chloride. The second mineral, 
amarantite, is probably identical with the first, although the author 
prefers to designate it by a separate name because of its different 
physical and chemical properties. Amarantite occurs in orange- 
colored microscopic crystals of the triclinic system.’ They have a 
citron-yellow streak, and a specific gravity of 2.11, and do not as 
readily undergo decomposition as does hohmannite.—Riebeckite. 
n a flesh-red granite from the Island of Socotro, in the Indian 
n, a hundred and fifty miles from Cape Gardafui, Sauer® has 
found a hornblende which corresponds exactly to aegerine among 
the augites. Its negative bisectrix (instead of positive as in the 
other horublendes) is inclined 5° to the vertical axis, its pleochroism 
is vr = dark blue; t = green; pi = blue, and its composition :— 
SiO, FeO, FeO MnO MgO CaO Na,O K,O 
50.01 2830 9.87 63 84 182 8.79 «7% 
Sauer calls attention to the fact, so often overlooked, that the for- 
mula of arfvedsonite, which is usually regarded as equivalent to 
aegerine, is based upon an analysis which is really that of aegerine 
* Amer. Jour. Sci., July, 1888, p. 57. 
* Bul. Soc. Franç. d. Min. x., p. : 5 
3 Seventh Ann. Rep. State Mineralogist, Sacramento, 1888, p. 205. 
* Min. u. Petrog. Mitth., ix., 1888, pp. 397, 42: 
5 Wiilfing: ib., p. 401. 
° Zeits. d. deutsch. geol. Gesell., 1888, xl., p. 138. 
