Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/348

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Mr. William Phillips on the Oxyd of Tin.

The above quotations from Dr. Berger's valuable paper are given solely with a view of shewing it to be his opinion that at least one district of Cornwall, producing tin, is not primitive. This has long been my opinion of that district, as well as of other parts of that county in which tin is found: and I cannot doubt but some specimens of granite in my collection from different places, enclosing tin, tend to confirm that opinion. But it may be well to await the development of many facts, which yet remain requisite to the better understanding of the geology of the county, as well as the light that might be thrown on the subject by a more perfect agreement in the use of geological language.

The existence of tin in the native or pure state is no longer believed. It was admitted by Romé de Lisle to have been so found, from the examination of a specimen from Cornwall under that name, which, by the description he has given of it, seemed to partake of the exterior appearance of molybdena. I possess a specimen of tin, found in the neighbourhood of St. Austle in that county, which with two or three others was arranged in the collection of my late uncle, now in my possession, under the name of native tin. It is almost coated by a ferruginous rust, and on one of its larger sides there are numerous portions of a very hard substance resembling iron, in which are embedded minute pieces of quartz; on this side I presume it to have been deposited. The fracture in some places is that of the finest steel-grained sulphuret of lead. The more pure parts of it easily flatten under the hammer, and fall off in small scales, which crackle between the teeth and easily yield to the knife. This specimen seems very much to agree with some found in France by Schreiber, an account of which he has given in the Journal des Mines, except that those were accompanied by a white substance, which proved to be the white muriate of tin.