That 65 carat 'zircon'

Tasmanian Gemstone and mineral specimen Prospecting

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blisters
Posts: 48
Joined: Thu May 19, 2016 11:40 am

That 65 carat 'zircon'

Postby blisters » Sun Feb 12, 2017 11:34 am

Well...... we got back home and did set specific gravity test on that stone and guess what it is not a zircon.

The test went as follows.
12.95 grams dry weight and into the 4 degree water.
Wet weight was 7.55, so the difference is 5.4.
12.95 ÷ 5.4 gives us 2.39

The only mineral that we can come up is Petalite with a SG of 2.39.
Attached is some more pics and info, and so we would be interested in hearing opinions!
Attachments
20170212_103859-1.jpg
20170212_110206.jpg
20170212_110250.jpg
20170212_104506.jpg
20170212_101518.jpg

digginhard
Posts: 25
Joined: Sat Dec 17, 2016 7:06 pm
Location: Derby.Tasmania

Re: That 65 carat 'zircon'

Postby digginhard » Sun Feb 12, 2017 3:11 pm

looks technical to me mate.Sorry all went a miss and I missed you guys the other day.Anyways I just wanted to let you know I picked up a 50ct zircon the other day with another 100 or so weighing at least 1-10ct out of one hole in a filthy little creek.Pics and weights to come.

blisters
Posts: 48
Joined: Thu May 19, 2016 11:40 am

Re: That 65 carat 'zircon'

Postby blisters » Sun Feb 12, 2017 8:11 pm

Cheers digginhard. No worries at all mate, looks like your looking in the right places and our paths will cross some time!

zzeehan
Posts: 15
Joined: Sun Feb 19, 2017 8:58 pm
Location: Hobart

Re: That 65 carat 'zircon'

Postby zzeehan » Wed Mar 08, 2017 10:15 pm

Hi pan4blisters,
Looks like a nice stone either way. Was wondering about the accuracy of the scales you were using to determine the SG?
A stated accuracy of 0.01g for any scales you intend using is what you are after, but remember, just because the scales have a LCD display showing two decimal places doesn't necessarily prove an accuracy of the same. Also, if your scales are a bit clunky or weren't calibrated it would be easy for your first decimal place to wander, too.
Your technique seems pretty good, I do see a lot of people doing SG's the hard way though. A simpler and accurate method requires an accurate carat scale, a small beaker/glass of water, a calculator and some fine cotton. See below.

Weigh your stone (aquamarine in this case): 2.06g
Tie some cotton to it
Zero a beaker of water on the scales
Measure the weight of the water displaced by totally immersing stone supported by cotton, just below surface, not touching anything: 0.76

Divide 2.06 by 0.76

Answer: 2.71

Walter Schumann, Gemstones of the World, says for aqua SG: 2.68 - 2.74
Bang in the middle.

Petalite has a perfect cleavage which you should see at least some evidence of in your stone when viewing with a 10x loupe.
If you are keen, try the SG technique above to confirm/disprove your previous calculation.

Regards
zzeehan
Attachments
calibration.jpg
Calibrate your scales using supplied weight(s) and the instructions that came with the scales
dry_weight.jpg
Weigh stone (aquamarine): 2.06g
zero_beaker.jpg
Zero a small beaker of water on the scales (my favourite shot glass, lol)
tie_stone.jpg
Tie some cotton to your stone
support_gem_with_cotton.jpg
Lower gem into beaker of water
weight_of_displaced_water.jpg
Measure the weight of the water displaced by totally immersing stone supported by cotton, just below surface, not touching anything: 0.76

blisters
Posts: 48
Joined: Thu May 19, 2016 11:40 am

Re: That 65 carat 'zircon'

Postby blisters » Mon Mar 13, 2017 9:03 am

Hi Zzeehan. Thanks for that much simplified method of doing the S G test, i thought there must be an easier way of doing it! :roll: I'll check the scales!

zzeehan
Posts: 15
Joined: Sun Feb 19, 2017 8:58 pm
Location: Hobart

Re: That 65 carat 'zircon'

Postby zzeehan » Fri Mar 17, 2017 11:21 am

No worries, Keep It Simple as they say!
Keep_It_Simple.jpg
Try some cotton, lol.

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