Correspondence. 245 
CORRESPONDENCE. 
On The Occurrence of Cubanite at Butte, Montana. Ex- 
. amination of a brass-yellow mineral that is now being mined for copper 
ore on the Speculator and Modoc claims near Butte, Montana, has led to 
the conclusion that the mineral is massive cubanite. 
Cubanite is a copper and iron sulphide having the composi- 
tion of Cu Fcg S4. Its theoretical composition is copper 20.87, iron 
36.93, and sulphur 42.24 per cent. Two analyses of this ore made by Mr. 
S. J. Gormly, chemist for the Anaconda Copper Mining Company, at 
the request of the writer, gave the following results : copper, 25.35, 
25.04, iron 34.90, 34,26, sulphur 39.05, 39,90, silica, 0.77, silver, 0.96 oz., 
and a trace of gold. The latter figure in each case is the more accurate. 
Other analyses not so reliable, reported to the writer showed 19.8 and 
23.6 per cent of copper respectively. The specific gravity is 4.26. 
In this analysis the copper percentage is high, being increased at the 
expense of the sulphur and iron. This is probably due to the presence 
of about 13 per cent, of bornite as a mechanical mixture, indications of 
the presence of that mineral having been noticed in the bright and 
variegated coloring of cleavage faces and joints. 
The uniformity of color, differing from pyrite and chalcopyrite, in 
large masses more or less mixed with vein quartz, and the closeness 
with which the composition approximates both the analyses given by 
Dana, and the theoretical composition, lead to the presumption that the 
mineral is of this species though no crystalline forms have as yet been 
perfectly identified. 
Its occurrence is in a vein which lies just north of a quartz porphyry 
dike, and parallel with it. It comes from the depth of about 200 feet. 
So far as the writer is aware this is the first cubanite locally reported 
in the United States. Horace V. Winchell. 
Butte, Afont. Aug. g, i8g8. 
Drift Formations of Long Island.— I have referred so often to 
the drift formations of Long Island in the American Geologist that I 
feel somewhat reluctant to call the attention of its readers again to 
the same subject. Some remarks, however, made by Prof. Salisbury 
in the Journal of Geology on certain criteria of stratified drift de- 
posits, which have only recently come under my notice, seem worthy 
of further remark. He says truly: "It is evident that the stratified 
drift may alternate with unstratified many times in a formation of 
drift deposits during a single ice epoch." I had some photographs 
taken to illustrate this very point along the terminal moraine in the 
city of Brooklyn. On the corner of St. Marks and Utica avenues 
where the altitude is about 160 feet above the level of the sea the 
complexity of the drift is very marked. Facing St. Marks, north side 
of the ridge, the stratification was exceedingly complex in character, 
the layers showing very much contortion, while just around the 
corner on Utica avenue facing west very little modification was visible. 
