The copper is mostly a copper glance passing into chalcopyrite; it is found in fissure veins with granite.
From copper-pyrites (chalcopyrite) iron-pyrites is distinguished by its superior hardness and by its paler colour.
The presence of copper, nickel and arsenic is possibly due in many cases to traces of kindred minerals, like chalcopyrite, pentlandite and mispickel.
Blende occurs in metalliferous veins, often in association with galena, also with chalcopyrite, barytes, fluorspar, &c. In oredeposits containing both lead and zinc, such as those filling cavities in the limestones of the north of England and of Missouri, the galena is usually found in the upper part of the deposit, the blende not being reached until the deeper parts are worked.
COPPER-PYRITES, or Chalcopyrite, a copper iron sulphide (CuFeS2), an important ore of copper.
Agricola; chalcopyrite (from XaXK6s, " copper," and pyrites) was proposed by J.
Chalcopyrite crystallizes in the tetragonal system with inclined hemihedrism, but the form is so nearly cubic that it was not recognized as tetragonal until accurate measurements were made in 1822.
Twinning according to the second law can only be explained by reflection across the plane (roi), not by rotation about an axis; chalcopyrite affords an excellent example of this comparatively rare type of symmetric twinning.
The mineral is especially liable to surface alteration, tarnishing with beautiful iridescent colours; a blue colour usually predominates, owing probably to the alteration of the chalcopyrite to covellite (CuS).
Chalcopyrite or copper-pyrites may be readily distinguished from iron-pyrites (or pyrites), which it somewhat resembles in appearance, by its deeper colour and lower degree of hardness: the former is easily scratched by a knife, whilst the latter can only be scratched with difficulty or not at all.
Chalcopyrite is decomposed by nitric acid with separation of sulphur and formation of a green solution; ammonia added in excess to this solution changes the green colour to deep blue and precipitates red ferric hydroxide.
Chalcopyrite is of wide distribution and is the commonest of the ores of copper.
The mining product next in value to coal in 1908 was copper, taken chiefly in Carbon county in a zone of brecciated quartzite underlying schist, the original ore being chalcopyrite, with possibly some pyrite, a secondary enrichment, which has produced important bodies of chalcocite in the upper workings, but these are replaced by chalcopyrite at greater depth.
The principal ores of copper are the oxides cuprite and melaconite, the carbonates malachite and chessylite, the basic chloride atacamite, the silicate chrysocolla, the sulphides chalcocite, chalcopyrite, erubescite and tetrahedrite.
Copper pyrites, or chalcopyrite, contains 34.6% of copper when pure; but many of the ores, such as those worked specially by wet processes on account of the presence of a large proportion of iron sulphide, contain less than 5% of copper.