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Below the zone of surface changes the ore of a copper vein is often a double sulphide of iron and copper called CHALCOPYRITE, a mineral softer than pyrite it can easily be scratched with a knife and deeper yellow in color.
The gold-bearing quartz veins of California traverse the metamorphic slates of the Sierra Nevada Mountains. But to the depth of about fifty feet from the surface the pyrite of the vein has been dissolved, leaving a rusty, cellular quartz with grains of the insoluble gold scattered through it.
In all cases this water contains a certain amount of gases derived from the decomposition of various substances, but principally from the alteration of iron pyrite, which affords sulphuretted hydrogen.
Another question which suggests itself in reference to the Leadville deposits is this: If the Leadville ore was once a mass of sulphides derived from the overlying porphyry by the percolation of surface waters, why has the deposit ceased? The deposition of galena, blende, and pyrite in the Galena lead mines still continues.
Planes or crystal ghosts, sometimes with pyrite crystals, marking stages of growth in the calcite crystals, are often distinguishable. The entire absence of anything like stalactites is noticeable, and together with the presence of the crystals, show that the cave was completely filled with water during their growth."
Ils sont aussi coupés dans leur intérieur, en sens différens, par d'autres plus petits filons, composés de matières très différentes; surtout d'une pyrite cuivreuse dure et pauvre, et que par cette raison on ne tente pas de séparer.
The benefit to Kolašin is obvious. At present the vast beech forests, literally rotting, could be utilised, for wood is dear in the barren districts of Montenegro. Pyrite, too, is found in great quantities. In fact, Kolašin is cut off from the rest of the country. Everything must be painfully carried on horses or mules, and for a woman, other than a peasant, it is a journey of great difficulty.
«La nature des filons du Rammelsberg est aussi différente de celle de Claustbat que l'est leur situation. C'est un massif compacte, et presque partout le même, de minéral de plomb et argent pauvre, pénétré de pyrite sulphureuse.
"Un phénomène encore plus curieux que cela est cette belle pyrite sulphureuse jaune, comme de l'or, qui est quelquefois parsemée par tout la substance de pétrifications agathisées, et qui apparemment y fut déposée après la dite métamorphose
It was noticeable, however, that the pyrite crystals which were free from zinc, galena, or other extraneous matter received no gold precipitate. Those which had such foreign associations were beautifully covered with fine gold crystals."
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