Nofe OH the Formation of Goltt Ore. — ran Kraatz. 103 
grains of pyrite. Solutions of dirt'erent strengths from 
-Wm tOTiMxxJ were filtered through the pyrite. The tiltrate 
showed no trace of gold by the tin chloride te«t (purple of 
Cassius test).* At my request Dr. F. Stockhausen repeated 
Johansson's experiment, with a similar result. He also found 
that lead, copper and antimony sulphids precipitate metallic 
gold from a solution of sodium auro-chlorate. That Johans- 
son's discovery of this method of the precipitation of gold 
from its chlorine solution has a direct bearing upon its occur- 
rence in ores of various localicies is suggested by its paragen- 
esis with chlorine-bearing pyromorphite in Wales, with 
chloridic mimetite of Nevada and chloridic vanadinite at Ber- 
josowsk. But however simple this explanation of the deposi- 
tion of gold by pyritic precipitation from its chlorine solutions 
may be, it is not applicable to the majority of cases. For 
frequently the chloridic minerals are wanting, and moreover 
the geld content of the rocks does not always decrease rapidly 
in depth, but very often remains practically constant to con- 
siderable depths. Here then we are obliged to turn for an 
explanation to quartz, the invariable associate of gold. 
Highly siliceous waters are found to-day in geysers and hot 
springs of North America. G. F. Becker investigated the hot 
springs of California with special reference to their content 
of dissolved metals. As described by him, the geysers of 
Steamboat Valley, Nevada, which are situated 11 km. north- 
westerly from Virginia City, at an altitude of 1,560 meters A. 
T., arise from a gray, coarse-grained, biotite hornblende gran- 
ite which is penetrated by fissures and overlain by andesytes 
and basalts. One series of fissures is filled by boiling, feebly al- 
kaline water that is sometimes thrown out in jets three or four 
feet high accompanied by a roaring noise. Another series of 
fissures which now exhale only steam with carbonic and sul- 
phurous acids, has, like the first series, covered its walls with 
hyalite, chalcedon}^ and crystalline quartz. In the siliceous 
sinter and decomposed granite are found sulphur, sulphates, 
iron oxides, cinnabar, manganese and traces of zinc, cobalt 
and nickel. In 403g of sinter the following were determined :f 
*"Mtlndliche Mittheilung:," bv K. Johansson. 
tEighth An. Ren. U. S. Geol. Sur. 1889, pp. 985, 967; see also J. Roth, 
Chem. Geolo^ne, Vol. Ill, p. .309. 
