The name is of Arabic origin and was long applied to crystallized pyrites (q.v.); it was restricted to the present species by W.
It is obtained commercially by roasting arsenical pyrites in either a Brunton's or Oxland's rotatory calciner, the crude product being collected in suitable condensing chambers, and afterwards refined by resublimation, usually in reverberatory furnaces, the foreign matter being deposited in a long flue leading to the condensing chambers.
Films of pyrites sometimes coat the joint-planes of coal.
Minerals which were not mined commercially in 1902 include asbestos, which occurs in Spartanburg and Pickens counties; fullers'-earth; graphite in Spartanburg and Greenville counties; iron ores in the north and north-west portions of the state; iron pyrites in Spartanburg and York counties; talc, bismuth, ochre, pyrites, ' galena, brown coal, malachite, phosphate of lead and barytes.
The compound FeS 2 is dimorphous, and the modern practice is to distinguish the cubic forms as pyrites and the orthorhombic as marcasite (q.v.).
Calcination is only advisable for ores which contain relatively much iron pyrites and little copper pyrites.
The pyrites is subjected to dry distillation from out of iron or fire-clay tubular retorts at a bright red heat.
The difficulty in separating zinc blende from iron pyrites is well known, and probably the most elaborate ore-dressing works ever built have been designed with this end in view.
In many cases it has been formed from other iron oxides, like haematite and magnetite, or by the alteration of pyrites or chalybite.
This operation is both more costly and more delicate than the roasting of pyrites, but it is now perfectly well understood, and gas is obtained from blende furnaces hardly inferior in quality to that yielded by pyrites kilns.