Laminated Quartz

The more we become acquainted with Mineralogy, the more we have to admire.

The nuclei of crystallization often form in plates; but, in the present instance, it should seem that, by some interruption of a particular nature in the dissolving menstruum, the crystal could not be formed so smoothly and regularly as is common with crystallizing Quartz, and tab. 199 shows that it may be mixed with much foreign matter without altering the regularity of the crystallization. Thus the present subject is the more remarkable, This sort of Quartz has been found pretty frequently at Glassteining, in Cornwall, but I do not know that it has been found elsewhere. It has often Tin and decomposing Feldspar about it; and whether the latter or any other decomposable substances have been originally formed with it, and have since caused its decomposition, as seems to be partly the case with the Pebbles tab. 103, either way it is a curious circumstance, and may lead to some useful truth in the investigation of the nature of Crystallography, or to some other part of mineralogical science.

These are the usual eighteen-sided crystals, interrupted in a peculiar manner.

The right hand figure is in plates a little oblique to the base of the pyramid, or to the transverse section of the column. The middle figure shows them still more oblique; and the left hand one shows the laminae disposed lengthwise to the column, with an interruption of another set of laminæ towards the top. The upper figure has many other varieties.

Most of the specimens which I have received of this curious subject are by favour of that warm friend to the science of Mineralogy, Philip Rashleigh, Esq.