Knowle Quarry Sample with blue-dye resin
Sample One
Sample One
Knowle Quarry Sample with blue-dye resin
Sample Tow
Knowle Quarry

Testing and Petrology

The thin sections of the two samples from Andy Gray’s quarry (Knowle Quarry)

The two Knowle Quarry samples consist of the same rock type – a lamprophyric rock of minette type.  Small altered phenocrysts of (?)pyroxene and biotite are set within an altered groundmass of K-feldspar, biotite and specular Fe(-Ti?) oxide.  There are also carbonate-(?)K-feldspar growths, which could represent either vesicle infills or an additional altered phenocryst phase (perhaps olivine).  One of the samples (the one that I have identified as ‘Knowle Quarry #2’) is more altered than the other and exists in a decarbonated state.  I attach a pair of microscope images (photomicrographs) showing the two stones in thin section; these are at the ‘same scale’.  Without going into great detail about what can be seen, note the areas of blue in the image of ‘Sample 2’ – these correspond to void space (now infilled by the blue-dye resin used during the sectioning process) and reflect the more altered, decarbonated state of ‘Sample 2’.

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