1893.] Mineralogy and Petrography. 385 
Moses" records the analysis of a granular nickel arsenide associated 
with native silver and siderite in a mine 18 miles west of Silver City, 
N. Mex. The silver is imbedded in arborescent forms in the brittle 
gray nickel ore, and this in turn is in a gangue of siderite. The 
analysis made on impure substance gave: 
je Pb Ag As Ni Co. Fe _ Total 
tr. 8.383 67.37 11.12 5.13 2.64=— 99.20 
Regarding the SiO, and Ag as impurities the iat aig takes a form 
that may be represented by RAs, in which R == 4 Ni 3 Co and } Fe, 
corresponding to a nickel skutterudite. 
On crystals of topaz from the Province of Omi and from the tin 
mines of Yenagari Mino, Japan, Matthew" finds four pyramids, seven 
prisms, one of which, æ Py, is new, the three pinacoids, three brachy- 
domes and two macrodomes. 
Optical Anomalies. — After an exceedingly careful examination 
of many sections of appophyllite crystals and a comparison of the phe- 
nomena they present with those presented by combinations of thin 
biaxial plates placed one upon the other, Klein concludes that the 
mineral in its geometrically tetragonal crystals is an intimate mixture 
of optically positive and optically negative triclinic lamelle. The 
positive constituent seems to differ from the negative element in con- 
taining no crystal water, since upon heating the positive component 
appears to increase in quantity. Negative appophyllite becomes posi- 
tive upon loss of 43 molecules of crystal water. The investigation is 
a beautiful piece of accurate optical work. 
In a reply to Mallard’s” remarks on the black -garnet pyrenaite 
Brauns” states that the structure described by the first mentioned 
anthor is exactly what should be expected of a dodecahedral substance 
under strain, and that the peculiarities of this garnet’s optical proper- 
ties may be easily explained on the Klein-Brauns theory of strain. 
Upon soaking in oil sections of zeolites that have been rendered 
cloudy by loss of water, they again become Snoen transparent for 
the study of their optical properties. Rinne” has taken advantage of 
School of Mines Quart., xiv, No. i, p. 49. 
"Iib, xiv, No. 1, p 
18Neues. Jahrb. f. Min., etc. oe II, p. 165. 
19AMERICAN NATURALIST, Oct., 1892, p. 849. 
_ Neues. Jahrb. f. Min., w, sens E pe 287. 
™Ref. ar Jahrb. f. Min., etc., 1892, II, p. 237. 
