320 Intelligence and Miscellaneous Articles. 



have seen other specimens from the same locality, but of inferior 

 value and beauty. 



b. The tetradymite from the Tellurium Mine, Fluvanna Co. Va., 

 and the native bismuth from the Peak of the Soratoin Bolivia, S. A., 

 are frequently interlaminated with gold. 



I have made some experiments with a solution of terchloride of 

 gold and tetradymite, and found that the latter precipitates the 

 gold from a dilute solution easily with a smooth and bi'illiant 

 surface. 



c. In the upper portion of the ore-bed in the metamorphic slates 

 at Springfield, Carroll County, Md., which, near the surface, consists 

 of magnetite and at a greater depth of chalcopyrite and other ores, 

 films of native gold have sometimes been observed coating the 

 cleavage-planes of magnetite. On close examination, it can be 

 perceived that below the film of gold the magnetite is oxidized into 

 hydrated sesquioxide of iron. 



d. A very striking occurrence of native gold is that where it is 

 associated with pyrites. Most of the pyritous gold ores are too poor 

 for us to form a positive opinion about the form in which they con- 

 tain the gold, from observation; and many authors are of opinion 

 that the gold may exist in the form of a sulphide, either by itself or 

 as a sulphosalt. If we take it for granted that the pyrites itself is 

 the result of the reduction of iron-salts, and bear in mind that pro- 

 tosalts of iron reduce gold instantaneously , we cannot adopt this 

 opinion. But even if terchloride of gold should have been precipi- 

 tated by hydrosulphuric acid whilst passing through the vein, it 

 could not remain in that state for a long time, because moist ter- 

 sulphide of gold in the presence of the smallest trace of an acid is 

 easily decomposed into metallic gold and sulphuric acid. Some 

 specimens of auriferous albite from Winter's vein, Calaveras County, 

 California, show beautifully that wherever there is a crystal of 

 pyrites, small crystals of gold are attached to it, demonstrating 

 that the sulphate of iron precipitated the gold previous to its own 

 reduction into pyrites. 



All these facts prove that the gold is carried into the veins from 

 the adjoining rocks, and that the opinion which considers veins the 

 source of the gold of alluvial and diluvial deposits and the soil is 

 erroneous. 



If another proof were wanted to show the fallacy of this idea, it 

 would be the fact that the gold from the soil or alluvial and diluvial 

 deposits has rarely the same fineness as that from the veins wrought 

 in the immediate neighbourhood of the same — the latter being 

 generally less fine. It is impossible therefore that the destruction 

 of a portion of these veins could have furnished the gold of such 

 deposits. — American Journal of Science and Arts, vol. xxviii. Sept. 

 1859. 



