Other copper minerals, such as the oxide cuprite and the sulfide chalcocite may require addition of oxidizing agents such as ferric sulfate and oxygen to the leachate before the minerals are dissolved.
12.
Malachite, azurite, cuprite Cu 2 O, pyromorphite Pb 5 ( PO 4 ) 3 Cl and smithsonite ZnCO 3 are stable in oxidising conditions and they are characteristic of the oxidation zone.
13.
Lapidary and decorative stone is varied and includes several types of attractive rock including serpentinite, leopard rock, jade, jasperized banded iron formation, and copper-coated ( malachite, chrysocolla, cuprite ) milky quartz.
14.
Though almost all crystals of cuprite are far too small to yield faceted gemstones, one unique deposit from Onganja in Seeis, Namibia, which was discovered in the 1970s, has produced crystals which were both large and gem quality.
15.
But although the cuprite studied at Arizona is not a superconductor, it revealed some properties likely to be useful in understanding cuprate superconductors, Dr . Colin J . Humphries of Cambridge University, England, wrote in commenting on the work.
16.
The copper oxide compound they studied ( a cuprite ) is not the same as the copper oxide compounds ( cuprates ) that conduct electricity without resistance at temperatures some 140 degrees Fahrenheit warmer than conventional superconductors, which can only function in extreme cold near absolute zero.
17.
Supergene profiles can be developed above weathered examples of IOCG deposits, as exemplified by the Sossego deposit, Para State, Brazil, where typical oxidised copper minerals are present, e . g .; malachite, cuprite, native copper and minor amounts of digenite and chalcocite.
18.
Associated copper minerals include the sulfides bornite ( Cu 5 FeS 4 ), chalcocite ( Cu 2 S ), covellite ( CuS ), digenite ( Cu 9 S 5 ); carbonates such as malachite and azurite, and rarely oxides such as cuprite ( Cu 2 O ).
19.
One decade later, a study of kohl manufactured in Egypt and India found that a third of the samples studied contained lead, while the remaining two-thirds contained amorphous carbon, zincite, cuprite, goethite, elemental silicon or talc, hematite, minium, and organic compounds.
20.
The number of faceted gems over two carats ( 0.4 gm ) is difficult to estimate, but according to Joel Arem, one-time curator for the Smithsonian National Gem and Mineral Collection in Washington DC, faceted cuprite of any size is considered one of the most collectible and spectacular gems in existence, with its deep garnet coloring and higher brilliance than a diamond.
