Sulphuret of Tin

This was, and still is, a rare substance, and is only yet known as found in Cornwall; first at St. Agnes in the time of the celebrated Klaproth, in a vein about sixty feet below the surface, and nine feet wide ; and since some has been found at Huel Scoria.

The upper specimen was brought from the former place, and, according to Klaproth, was found in what is called Growan by the Cornish miners, which is decomposed Feldspar of the Granite rocks:—see tab. 224. Rasp, who resided in Cornwall at the time, gave it, because it contained much Copper, the name of Bell Metal Ore. To Bell Metal it bears some resemblance, and is brittle like that. In so large a vein it must be supposed to vary a little, being occasionally grayer or yellower, with more or less Copper. Klaproth observes that Rasp's name would be more just if there were a larger proportion of Copper to the Tin. The varieties of course admit of some allowance, and each may be right; but their specimens probably differed.

The lower figure is of a regular texture and smaller grain; it came from Huel Scoria, by favour of my kind friend Mr. R. Phillips. There is among it something like Mispickce, or Arsenical Iron, of a grayish white colour:—see Descr. tab. 150. It has a bloom and dark tarnish on the outside. I was lately favoured with a specimen by my kind friend the Rev. W. Gregor, from Huel Rock in St. Agnes’s parish, which is a mixed specimen, including Sulphuret of Copper and Iron. It had some indications of the Growan matrix about it.

Klaproth’s analysis seems perfectly to agree with this substance, as under:

It is arranged by most authors as Sulphuret of Tin, although this analysis gives more Copper than Tin; but the Copper is generally thought to be merely mixed with the Sulphuret of Tin: indeed its granular texture prevents a complete separation from tire Copper Pyrites that accompanies it.