Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/351

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341
Mr. William Phillips on the Oxyd of Tin.

The oxyd of tin sometimes occurs in form and appearance very similar to the hematitic iron ore, from which it is easily distinguished by its superior weight. In this state it is mostly in fragments, either straight or diverging, wedge shaped or splintery, rarely rounded and reniform; those fragments of which the fracture is fibrous, have a silky lustre; its colour is brown of different shades, passing into brownish-yellow, which are ranged in alternate bands; it gives a shining yellowish-brown streak, and is opaque, hard, brittle, and easily frangible; its spec. grav. is 6.45. This mineral from its occasional resemblance to wood, has obtained the name of wood tin, and is the Kornisches zinnerz of Werner, the Etain oxydé concretionné of Haüy. Before the blowpipe it becomes brownish-red and decrepitates, but is not fused or reduced to a metallic state: when strongly heated in a charcoal crucible, it affords, according to Klaproth, 73 per cent. of reguline tin. It has hitherto been found only in Cornwall, in the parishes of St. Columb, St. Roach and St. Dennis, in alluvial beds accompanied by stream tin; it is rare, and occurs only in small pieces.[1]

Klaproth mentions “a kind of wood tin, from Maddern in Cornwall. This is only found in small separate hemispheres, of the size of a divided shot. The surface is smooth and brown, but the inside or nucleus is of a light brown and of a whitish-yellow colour, and slightly radiated. These stalactitical hemispheres, which, as one may see, have been fixed to other bodies, are similar to the small spherical protuberances of wood tin, except that the latter are not so hemispherical, but flatter.”[2] This substance, I do not remember to have seen in the form above described, but some rounded portions of tin were given to me by a Cornish gentleman

  1. Aikin Chim. Dict. art. Tin.
  2. Klaproth on Fossils of Cornwall, p. 21.