Copper
Cu
atomic number
29
melting point
1084.62°C

1. Roast a small amount of powdered mineral sample on charcoal using the oxidizing portion of the flame, then mix the roasted sample with borax flux (actually, a 1:1 mixture of borax and sodium carbonate works best) and heat it on a charcoal block using the reducing portion of the flame; a bead of metallic copper will be produced.

2. Mix a small amount of roasted mineral powder with borax flux, then immerse the mixture in the oxidizing portion of the flame; the fused bead will be green when hot and blue when cold; if the reducing portion of the flame is applied to the bead, it will turn very pale if only a small amount of copper is present; if the sample is high in copper, it will turn an opaque red in color.

3. Intensely heat a pinch of copper-bearing mineral sample with a lamp, candle, or Bunsen gas burner; the flame will turn a beautiful emerald-green in color; if the sample is first roasted, then moistened with HCl and re-exposed to the flame, it will impart a rich azure-blue color to the flame; (this procedure can be employed on samples of cuprite and all oxidized copper-bearing sulfides).

4. Dissolve the powdered mineral sample in nitric acid (HCl will work for some copper-bearing minerals); the solution will take on a light blue to bluish-green color; add excess ammonia to the solution and a striking color change occurs; the solution takes on an intense blue color.