244 ^^^^ American Geologist. October, looi. 
niav have included, as estimated liy Dana, Walcott, and others, 
about one hundred or two htuKh^ed million years. 
If a much longer time than the 7,000 years estimated in 
this paper should be admitted for the duration of the Niagara 
river and the Postglacial period, as Spencer and Taylor sup- 
pose, all the terms of this g'eologic series making up the age of 
the earth must be proportionallv multiplied five-fold or seven- 
fold. The whole would then pass far beyond the maximum 
limit which seems to have been relial)ly determined by the re- 
searches of geology, astronomy, and plivsics. 
NOTE ON CERTAIN COPPER MINERALS.* 
By Alexander \'. Wincheli., Butte, Montana. 
Chalcopyrite has been noted more than once as an acci- 
dental product in metallurgical operations. Thus, Hausmannf 
described it as resulting from imperfect roasting of cop- 
per bearing ore at the works in Goslar and in Ocker. The 
mineral was here found in crystals exceeding five millimetres 
in largest diameter, twinned and striated : the crystals were 
of a fine black color, and a little altered on the surface. 
Plattner:}: noted similar crystals in a crack in the bed of 
a reverberatory furnace at Mulden near Freiberg. These 
crystals contained, according to analysis, a slight excess of 
iron, and small amounts of foreign metals. 
So far as known to the writer bornite has never been 
described as an accidental furnace product, nor as produced 
artifically by sublimation. Its reproduction has been accom- 
plished only, by fusion, or by the action of thermal springs 
upon bronze. 
It is intended here to describe an occurrence of. chalcopyrite 
and bornite at the smelter of the Butte & Boston Consolidated 
Mining Co., at Butte, Montana. The minerals form slowly, 
attaining their maximum thickness of about four inches in the 
course of six months to a. vear. They form in the Allen- 
*Read at the Denver meeting of the American Association (or the Advance- 
ment of Science, August, 1901. 
f Haurmann: — Goett. f::elehrt. Nadir., 1S52. No. 2, p. 177, Ref. from Encyc. 
Chimique. Bouki-.eois : — Reproduction artificielle des mineraux, p. 45. 
If FucHS: — Die kunst. darg. Min., p. 62, ref. from same source. 
