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<p>[QUOTE=&quot;Bronwen, post: 3051523, member: 5833&quot;]I&#039;m willing to believe it is not plastic, even without the hot needle test that would have left a melted pinhole in the material if it had been plastic.&nbsp; </p><p><br /></p><p>Glass is not that much softer than black onyx, which is a form of quartz.&nbsp; A sharp object that is not applied hard enough will not scratch glass.&nbsp; A sharp object applied with enough force will scratch onyx.&nbsp; The difference in pressure needed is not huge.&nbsp; </p><p><br /></p><p>Did the jeweller do this by hand?&nbsp; Was he really willing to leave a scratch across the back to prove glass?&nbsp; Would he have risked scratching stone?&nbsp; If he had made a scratch, could he have been perfectly certain he had not scratched hard enough to scratch onyx?&nbsp; It&#039;s a very imperfect, imprecise test.&nbsp; I can imagine the jeweller, not wanting to scratch stone, not scratching hard enough for glass.</p><p><br /></p><p>Lastly, does your jeweller really believe this was cut in relief, with that stippled background, in stone?&nbsp; </p><p><br /></p><p><img src="https://www.antiquers.com/attachments/14d-3-jpg.291128/" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><br /></p><p>If it were an intaglio, with the design ground down into the surface I could see the possibility of stone.&nbsp; But it is a cameo meant to look like an ancient coin.&nbsp; This would be very complicated to cut in stone, very easy to mold in glass.&nbsp; I&#039;m afraid I do not think your jeweller&#039;s testing is reliable.[/QUOTE]</p><p><br /></p>

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