Pointed Schorle Enlarge
Dec 1 1810 published by Js Sowerby London.
British Mineralogy
CCCLXXXIX
Argilla electrica

Pointed Schorle

Among the many forms that this substance assumes, and not rarely, is the present; but it has not yet been described, to my knowledge. It is composed of elongated prisms, a smaller or greater number of which commencing at a point, often diverge to great lengths, thickening more or less regularly, as figured. I have them mostly six-sided, with some of the angles here and there truncated longitudinally, so that some have as many as twelve sides, giving the appearance of a peg cut in angles and left without being rounded. I expect they are often of great length: what I have are only about three inches long (sent me by the Rev. Patrick Forbes lately mentioned), but these have no terminations. They sometimes, however, end abruptly, as the hollow impressions show: they sometimes also have a transverse cracky which is filled up with Quartz. Indeed it does not appear to me that any one has yet made a research for the purpose of investigating to what length Schorle may shoot or lengthen: perhaps this may be a hint towards some attempt of the kind; which, how ever, is the more difficult as it is so frequently among Quartz in the hard Granite Rocks: when, however, it is found among the more micaceous parts of it in veins, it may be better traced, as in such situations it is often very long, but perhaps seldom so perfect.

I was favoured with the upper specimen by the Earl of Seaforth? from the neighbourhood of Portsoy in Banffshire. In it the Schorle is passing through or among Felspar or Kaolin and Quartz, leaving its impression where it has become detached, which is often the case, as in some parts it is almost loose, with Mica interposing between it and the Quartz. I add the lower specimen as a remarkable variety among shattered Quartz, diverging and divaricating in fasciculated prisms almost approaching to spiculæ; the principal Quartz fracture being on one side or at right angles with them or nearly so, as if formed in another direction. This is from Aberdeen.

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