stokes] MISCELLANEOPS SPECIMENS. 87 
••This specimen is derived from the Present Need mine, Quartzburg district, 
( {rant County, Greg. The vein, carrying chiefly gold, partly in free form, partly 
associated with sulphides, is contained in diabase and diabase-porphyry. The ore 
minerals are normal yellow pyrite, a soft, yellowish-gray material supposed to be 
marcasite, zinc blende, and chalcopyrite." The iron sulphides are easily separated 
from the rock and other sulphides by hydrofluoric acid. The yellowish-gray 
material, which is closely veined with pyrite, could not be separated from the 
latter, but the oxidation coefficient of the mixture indicates that it is marcasite. 
The portion examined contains a trace of copper and lead and no zinc. 
.No. 19. This is thus described by Mr. Lindgren: "This specimen is taken from 
the dump of the Chautauqua tunnel, at De Lamar, Owyhee County, Idaho. The 
specimen consists of quartz , upon which there is a crust of pyrite. The quartz 
itself contains arborescent forms of a mineral supposed to be marcasite and 
described as such in Twentieth Annual Report U. S. Geological Survey, Part Ill- 
page 130." The mineral in question was easily separated from the quartz and the 
mass of the pyrite by digestion with hydrofluoric acid. It formed dark-colored 
tabular masses, presenting no definite crystalline form, and containing traces of 
copper and lead with a notable amount of arsenic. The oxidation coefficient 
(51.3) shows that it consists of at least 93.5 per cent of pyrite, but the pro- 
portion thus determined is somewhat too low. owing to the influence of the 
arsenic. 
No. 20. Thus described by Mr. Lindgren: '-This specimen is taken from the 
Garfield tunnel, 350 feet from the portal, near De Lamar, Owyhee County, Idaho, 
and is described on pages 131 and 171, Twentieth Annual Report U. S. Geological 
Survey, Part ill. The specimen consists of a soft white material, which, accord- 
ing to analysis, is probably kaolinite mixed with sericite. It contains arborescent 
forms of marcasite."' The supposed marcasite was isolated by hydrofluoric acid. 
It could not be definitely described as such from the color and crystalline form. 
As the oxidation coefficient (19.8) was too high for pure marcasite, a portion was 
mixed with one-ninth its weight of pyrite, and then gave— 
p=22.6=41 per cent pyrite. 
We have, then — 
0.9 x+ 10=41, or #=34.4. 
This corresponds to p=20A\ a number agreeing within permissible limits with the 
original determination. We have, therefore — 
Pei' cent. 
Pyrite directly determined __ 30.5 
Pyrite indirectly determined 34. 4 
and the original conclusion of Mr. Lindgren is only in part confirmed. A little 
arsenic is also present. 
No. 21. Material supposed to be marcasite, from South Dakota. Submitted by 
Dr. G. P. Merrill. The sample consists of spherules not over one-half millimeter 
in diameter and so brittle as easily to be crushed by the finger. They had under- 
gone vitriolization to such an extent that the original substance was entirely con- 
cealed in the mass of sulphate. The oxidation coefficient shows that the material 
is pyrite, and the analysis that some copper is present. The normal value of p 
indicates that the copper is probably in the form of chalcopyrite. 
No. 22. Marcasite from Littmitz, 1 Bohemia, consisting of flat, deeply striated 
twins of marcasite on a nucleus which on fracture shows both marcasite and 
1 Regarding the Littmitz marcasite, see Sadebeck, Monatsber. K. preuss. Akad. Wiss. Berlin, 
Vol. XX, 1878, p. IS), and Hintze, Handbnch der Mineralogie, Vol. I, pp. 7:52, 825. 
