Sulphuret of Iron. Pyrites

The upper figure is from Cornwall.

This substance is very universal, and not rarely occurs crystallized. It is perhaps as often found in the cubic or primitive form as any thing we know of, especially among the schistose rocks in Wales, Scotland, Cornwall, and Ireland, on what Dr. Babington denominates Calp, vulgarly called Irish Diamonds. This sort was used formerly for making buttons, and was in fashion as jewellery for ladies’ ornaments about half a century ago, being cut and polished by the lapidaries for that purpose, often to the destruction of the natural crystal. It is often found among coals, &c. It forms many varieties of crystallizations. The upper figure shows a group of cubes: the larger one appears somewhat laminated in the structure, and is nearly covered as it were with a thin case. They are often quite smooth, but are more frequently found with straight lines or striæ on the faces, altering with the faces next to each other, but agreeing with the opposite sides or faces. The cubes are often larger than those here figured.

Under the blowpipe the odour of sulphur is very sensible, and a magnetical oxide of iron is to be produced. It scintillates with steel.

The lower figure from Redrugh, in Cornwall, with little cubes, piled like clubs, and somewhat varying in colour, perhaps contains a little more copper. Mr. Kirwan says a small portion of copper is always present in pyrites. The upper part being paler than the lower is a sort of indication fo its holding most iron. Spec. Grav. 4,1006–4,7491.