Ligniform Quartz Enlarge
Feb 1. 1813 published by Jas Sowerby London.
British Mineralogy
CCCCLXXIII
Silex quartzum, ligniforme

Ligniform Quartz

  • Div. 2. Imitative. Wood-like.

The curious attenuated thready and cottony appearance of this Quartz has been so much admired, that I thought it would be wrong in me to withhold a representation of it, as it may prove extremely instructive; for at first it looks so unlike what it really is, that it becomes necessary to be apprized of it, and to attend to it some time to discover what it is. It is very white, nearly opaque Quartz that has been infiltrated into the pores of wood in such a way as to allow the wood to escape, and is so incorporated as to remain a representation of the wood as if it were still existing in the specimen. The fibres are, however, so slightly attached to each other near the outside, that the specimen is continually falling to pieces; but they become closer and more firmly attached towards the inside, where it is pretty nearly in a compact state at present; but I suspect that some Sulphuret of Iron or other decomposing substance is mixed with it, and will eventually cause the whole to fall to pieces. It appears to be mostly destitute of the transverse fibres. Its asbestus-like or amianthine aspect has deceived many.

I have met with nearly the same thing before in Carbonate of Lime, but of a brown wood colour, in a specimen from Worton in Oxfordshire, by favour of C. Stokes, esq.; but this is not quite so easily decomposed: it occurs also imbedded in a Siliceous Marly Stone at Nut field, and this is very crumbly; they are also softer to the touch; whereas the white specimen is harsh and rigid to the touch, very like Actinolite, and, like that, acts as Cowhage does upon the skin.

The specimen Mas sent by Miss E, Hill from the Whetstone pits at Blackdown near Cullumpton in Devonshire.

The Worton specimen is figured on the right hand for comparison: in it the bark appears to have been succeeded by Crystallized Carbonate of Lime.

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