Gemstones & Jewellery > Gemstone Discussions

How to measure Specific Gravity

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Aussie Sapphire:
Merryn passed on this document from the old version of Tip Top Gems blog - Dave from Tip Top Gems has kindly allowed us to put this on ALF as a reference for our members.

Basically, it is a step by step guide on how to measure specific gravity using your digital scales.  We have discussed this before but this is a great instruction guide with heaps of photos to show you exactly how to go about it.

NEW LINK here:
http://aussielapidaryforum.com/forum/index.php?action=downloads;sa=view;down=9

SG is a fantastic diagnostic and easy to do once you have your rig set up so why not give it a try.

Some SG values can be found here:
http://nature.berkeley.edu/classes/eps2//wisc/sg.html
http://www.gemselect.com/gem-info/specific-gravity.php

Click here to see the new version of Tip Top blog - the Gem Vault

cheers
Leah


Edited by admin to correct the document link.

oldlrnut:
Hi Leah,
I remembered that document from way back in the forum and actually used it this morning in an attempt to identify some non transparent greenish material from Grabben Gullen. SG ended up as 2.62, it is softer than quartz and has a sort o linear cleavage. Still a mystery.
Cheers,
Allan

mehoose:
Allen, first off we know that SG is more of a ruling out tool. No one test is used for a definite ID.
WHat I'd be tempted to do next is test the SG of a definite know rough type. Topaz, quartz etc to make sure it falls into it's parameter to rule out scale issues.
What you have presented falls into a few groups, chalcedony 2.60+/-.05, Serpentine 2.57+/-.06, scapolite 2.68+/-.06. It does seem a bit high for Variscite which is 2.50+/-.08.
Is it solid green or something else scattered in it. If it doesn't look like chalced or variscite i'd be saying Serpentine. There are plenty of different types. Will try and see if I can find a bit more about the specific area.

Wwoofa:
Hi,
I just used the technique described instead of using my balanced scales and it was much easier & more accurate.
Thanks to Leah, Merryn & Dave for making the doc available.
Regards, Paul

Plutonium:
Eureka !

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