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<p>[QUOTE=&quot;desertgem, post: 741380, member: 15199&quot;]Welcome to the forum. Determining specific gravity requires that one has the weight of the sample as well as the volume. The weight can be determined easily, the volume of a sample with uneven surfaces something else. So for volume, usually a water displacement is used. The volume of water displaced can be measured by accurate syringes, or by weight of the water.&nbsp; The most common way is to use the weight of the object out of water compared to the weight of the object under water. Here is a url for a relatively inexpensive SG kit. </p><p><a href="http://www.mineralab.com/Specific%20Gravity.htm" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.mineralab.com/Specific%20Gravity.htm" rel="nofollow">http://www.mineralab.com/Specific%20Gravity.htm</a></p><p><br /></p><p>When I do sp. gr. I use a modified Mettler balance with a 2 tier pan, the lower tier below water level. I get dry weight by measuring the weight in the upper tier of the pan( above water) and then transfer the object to the lower part of the pan under water for the second weight. It is overkill for coins that are very large compared to gemstones, but it still works when I need it.</p><p><br /></p><p>Jim[/QUOTE]</p><p><br /></p>

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