F. A. Genth’s Contributions to Mineralogy. 255 
showing very distinctly one rhombohedron, scalenohedron and 
an; it is coating tetradymite and ‘evidently a pseudo- 
morph after it. I have seen other specimens from the same 
locality, but of a value and beauty. 
b. The tetradymite from the Tellurium Mine, Fluvanna Co. 
Va., and the native bismuth from the Peak of the Sorato in 
Bolivia, S. A., are frequently interlaminated with go 
ve made some experiments with a solution of terchlorid 
of ea and tetradymite and found that the latter precipitates 
ihe ge gold from a dilute solution easily with a smooth and brilliant 
surface. 
c. In the upper portion of the ore bed in the metamorphic 
Mics . Springfield, Carroll county, Md., which, near the sur- 
face, consists of magnetite and at a greater depth of chalcopyrite 
and other ores, sometimes films of native gold have been ob- 
served coating ‘the cleavage planes of magnetite. On close ex- 
amination it can be noticed that below the film - — the mag- 
hetite is oxydized into hydrated sesquioxyd o 
d. A very striking occurrence of native gold i is, ;, that where it 
is associated with pyrites. Most.of the pyritous gold ores are too 
poor to form a positive opinion about the form, in which they 
Contain the gold, from observation, and many authors are of 
Opinion that the gold may exist in the form of a sulphid, citer 
by itself or as a sulphosalt. If we take it for granted that 
pyrites itself is the result of the reduction of eae and bear 
in mind that protosalts of iron reduce gold #% 
Cannot adopt this opinion. But even as ease Ae gol vald-at abaeld 
have been precipitated by sulphydric acid, whilst Agrees 
through the vein, it could not remain in that state for a lon 
time, because moist tersulphid of gold in the presence of fae 
smallest trace of an acid is easily decomposed into metallic pis 
and sulphuric acid. ras specimens of auriferous albite from 
Winter's vein, Calayeras county, California, show beautifully 
that, wherever there is a erystal of pyrites, small crystals of gold 
are attached to it, demonstrating, t dot the sulphate of iron pre- 
Cipitated the gold, previous to its own reduction into pyrites. 
All these facts prove that the gold is carried into the st 
from the adjoining rocks, and that the opinions which 
Veins the source of the gold of alluvial and diluvial deposits ts and 
the soil, is erroneous. 
If another proof was wanted to show the fallacy of this idea, 
it would be the fact that the gold from the soil or alluvial and 
eavial deposits, has rarely the same sneea. a as that from the 
- Me ‘ns wrought in the immediate neighborh« od of the same, the 
[latter bea 1. Senarally less fine, It is Sapoaible therefore that 
) ~— the destruction of a porti sine of these veins could have furnished 
phia, July 27, oe - 
