i82 The American Geologist. m^'"*^^- i^oi. 
the formation toward the south-east. The new mineral mohawkite oc- 
curs in a vein at the Mohawk mine associated with other copper arsen- 
ides in a gangue of quartz and calcite. The mineral is massive, struct- 
ure granular to compact, color a gray tinged with yellow taking readily 
a brassy to purplish tarnish. It is brittle, hardness about 3.5 with a 
specific gravity of 8.07. A chemical analysis gives its composition as 
follows: Cu=6i.67, Ni=7.03, Co=2.20, Fe= trace, As=28.85, which 
gives the mineral the formula (Cu, Ni, Co)3As. The author shows 
also that nickel and cobalt are present in small quantities in the miner.1l 
domeykite CusAs, and, that the specific gravity of the latter should be 
7.94 instead of 6.7 to 7.5 as given by the mineralogies. By volatilizing 
arsenic over red hot copper in a combustion tube sealed at one end two 
arsenides were obtained, one having the composition CuiAs and re- 
sembling chalcocite, the other consisting of groups of minute crystals 
and identical with domeykite in composition. By the name stibio- 
domeykite the author designates a mineral from the Mohawk mine 
closely resembling domeykite but containing a small percentage of 
antimony ; and by the name mohawk-whitneyite a very intimate mix- 
ture of the two minerals mohawkite and whitneyite. The results of 
several analyses of these last mixtures accompany the article. The cor- 
rectness of the formula (Cu Ni Co)4As, which was assigned to mo- 
hawkite by Dr. Ledoux and reported in the April number of the Min- 
ing Jou7-nal for 1900, is strongly denied by Dr. Koenig. He concludes 
his paper with a new analysis of algodonite, confirming the formula 
CueAs. Its specific gravity was found to be 8.383 instead of 7.62 as- 
previously given. c. h. vv. 
The analyses of Italian volcanic rocks. By H. S. Washington. (Atn. 
J. Sci., 159, 44-45) 
Analyses are given of the following types of rocks : ciminyte, from 
Monte Cimino, Viterbo ; mica trachyte (selagyte), from Monte Catini, 
Tuscany; andesyte, from Radicofani, Tuscany; leucityte, from Capodi 
Bove, Alban Hills. A discussion is made of the analyses, the miner- 
alogical composition of the rocks and their classifications in accord- 
ance therewith. c. h. w. 
Occurrence of native lead with copper and other minerals at Franklin 
Furnace, N. J. By W. M. Foote. {Am. J. Sci. 156, 1^-188.) 
Small irregular masses of lead i to 2 mm. in diameter, associated 
intimately with native copper and a variety of minerals — among them 
axinite, garnet, willemite and phlogopite — have been found on a few 
specimens taken from the 800-foot level of the Parker shaft on North 
mine hill. The rarity of native lead and its associations at Franklin 
make the discovery interesting. c. H. w. 
Occurrence of sperrylite in North Carolina. By W. E. Hidden. (Am. 
J. Sci., J56, 380-381.) 
The mineral sperrylite a di-arsenide of platinum — is described from 
Macon county, N. C, where it was discovered in the sands of Cowee 
creek, associated with a little gold and the minerals monazite, zircon 
and menaccanite. The sperrylite consisted of a few very minute, nug- 
