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<p>[QUOTE=&quot;Bronwen, post: 999655, member: 5833&quot;]Author makes this statement, &#039;Pure black chalcedony is rare&#039;, but does not support it in any way.&nbsp; It may be out there somewhere, but it is safe to assume that any hardstone cameo with a black layer has been treated.&nbsp; Any time the color is deep &amp; even, dye has to be suspected.&nbsp; I put some photos of cameos in untreated stone at the end for comparison.</p><p><br /></p><p>This, &#039;by definition, onyx should have straight parallel stripes of black and white&#039;, is true insofar as in the glyptics world &#039;onyx&#039; is used in combination, not by itself.&nbsp; The non-white layer does not have to be black.&nbsp; The notion that the distinction between &#039;onyx&#039; &amp; &#039;agate&#039; is whether or not the color layers are &#039;wavy, curved, or irregular&#039; is an eccentric one; the material is routinely called &#039;banded&#039; or &#039;ribbon&#039; agate when the layers are straight &amp; parallel.</p><p><br /></p><p>Without photos, I&#039;m not even sure what author is writing about.&nbsp; From opening, I would have thought topic was the solid colored stone used for all those flip rings with a little diamond set in black stone on one side, often a cameo on the other.&nbsp; Then there&#039;s something about what to call it if a stone that is naturally black &amp; white has been dyed to all black.&nbsp; Then we&#039;re off to druse crystal formations &amp; the arbitrary nature of modern cameo prices.&nbsp; Just as well he did not explain nicolo.</p><p><br /></p><p>This bit mystifies me completely:&nbsp; &#039;Polished black onyx scratches fairly easily and the scratches are noticeable, which is why most carvings are matte-finished.&#039;&nbsp; They are?</p><p><br /></p><p>This illustration shows some of what the JCK author is describing. The section labeled &#039;a&#039; was left in its natural state; all others were subjected to one treatment or another, most involving saturation with a solution &amp; heat.&nbsp; Different layers have different degrees of porosity, leading to the different results given by the same treatment.</p><p>[ATTACH=full]206492[/ATTACH]</p><p><br /></p><p>Grabbing an assortment from my Bacchus file, just to show that not all hardstone cameos are so tidy:</p><p><br /></p><p>[ATTACH=full]206495[/ATTACH] [ATTACH=full]206496[/ATTACH] [ATTACH=full]206497[/ATTACH] [ATTACH=full]206498[/ATTACH] [ATTACH=full]206499[/ATTACH][/QUOTE]</p><p><br /></p>

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