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<p>[QUOTE=&quot;Bronwen, post: 10467878, member: 5833&quot;]As with acid testing of metals, I&#039;m still trying to understand what readings on a Presidium gem tester can mean.&nbsp; From some quick Googling, what is measured is not hardness or refractive index but thermal conductivity.&nbsp; Diamonds are extremely good conductors of heat, and most of what comes up at the top of the search results concerns the Presidium tester&#039;s ability to distinguish diamond from everything else.</p><p><br /></p><p>For lesser gems, some of the ranges, particularly the garnet group, are very wide; only the most common precious &amp; semiprecious gem names are used as range labels; and, other than glass, the names of man made materials are not used in range labels, so it&#039;s not clear how a CZ would read.&nbsp; <img src="styles/default/xenforo/smilies/confused.png" class="mceSmilie" alt=":confused:" unselectable="on" /></p><p><br /></p><p>The properties of CZ seem a bit paradoxical to me, as there does generally seem to be a degree of correlation between hardness &amp; thermal conductivity.&nbsp; But, while CZ has about the same hardness as garnet, its thermal conductivity is relatively low.&nbsp; All in all, it looks to me like a CZ would register at best at the low end of the garnet range.</p><p><br /></p><p>My gem book describes almandine garnet as being &#039;red with a violet tint&#039;; pyrope is &#039;red with brown tint&#039;.&nbsp; The refractive index, the measure of sparkle, is higher for almandine garnet.&nbsp; I don&#039;t know whether yttrium aluminum garnet (YAG) comes in colors, but it has a refractive index a little higher than that of almandine garnets.</p><p><br /></p><p>While poking around, came across this chart on Presidium&#039;s site. I imagine it probably comes with the gadget, but have attached the file for the rest of us.[/QUOTE]</p><p><br /></p>

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