Copper sulfide is a copper sulfide

Copper sulfide

Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores....

, a chemical compound of copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 and sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

. It has the chemical compound Cu₂S. It is found in nature as the mineral chalcocite

Chalcocite

Chalcocite, copper sulfide , is an important copper ore mineral. It is opaque, being colored dark-gray to black with a metallic luster. It has a hardness of 2½ - 3. It is a sulfide with an orthorhombic crystal system....

. It has a narrow range of stoichiometry ranging from Cu_1.997S to Cu_2.000S.

Preparation and Reactions

Cu₂S can be prepared by heating copper strongly in sulfur vapour or H₂S. The reaction of copper powder in molten sulfur rapidly produces Cu₂S, whereas pellets of copper require much higher temperature
Cu₂S reacts with oxygen to form SO₂:

2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂

In the production of copper two thirds of the molten copper sulfide is oxidised as above, and the Cu₂O reacts with unoxidised Cu₂S to give Cu metal:

Cu₂S + 2Cu₂O → 6Cu + SO₂

Structure

There are two forms of Cu₂S a low temperature monoclinic form ("low-chalcocite") which has a complex structure with 96 copper atoms in the unit cell and a hexagonal form stable above 104°C. In this structure there are 24 crystallographically distinct Cu atoms and the structure has been described as approximating to a hexagonal close packed array of sulfur atoms with Cu atoms in planar 3 coordination. This structure was initially assigned an orthorhombic cell due to the twinning of the sample crystal.

There is also a crystallographically-distinct phase (the mineral djurleite

Djurleite

Djurleite is a copper sulfide mineral of secondary origin with formula Cu31S16 that crystallizes with monoclinic-prismatic symmetry. It is typically massive in form, but does at times develop thin tabular to prismatic crystals. It occurs with other supergene minerals such as chalcocite, covellite...

) with stoichiometry Cu_1.96S which is non-stoichiometric (range Cu_1.934S-Cu_1.965S) and has a monoclinic structure with 248 copper and 128 sulfur atoms in the unit cell . Cu₂S and Cu_1.96S are similar in appearance and hard to distinguish one from another.

See also

• copper sulfide
  Copper sulfide
  Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores....
  
   for an overview of all copper sulfide phases
• copper monosulfide, CuS
• Chalcocite
  Chalcocite
  Chalcocite, copper sulfide , is an important copper ore mineral. It is opaque, being colored dark-gray to black with a metallic luster. It has a hardness of 2½ - 3. It is a sulfide with an orthorhombic crystal system....
  
  
• Djurleite
  Djurleite
  Djurleite is a copper sulfide mineral of secondary origin with formula Cu31S16 that crystallizes with monoclinic-prismatic symmetry. It is typically massive in form, but does at times develop thin tabular to prismatic crystals. It occurs with other supergene minerals such as chalcocite, covellite...