collapse

Author Topic: Specific Gravity test  (Read 827 times)

Percy1

  • Newbie
  • *
  • Posts: 2
    • View Profile
Specific Gravity test
« on: June 01, 2019, 06:27:08 PM »
Just new at identifying sapphires and was wondering if someone could explain what and how you do a Specific Gravity test thanks.

Aussie Sapphire

  • Administrator
  • ALF'er VIP
  • *****
  • Posts: 3300
    • View Profile
    • Aussie Sapphire
    • Email
Re: Specific Gravity test
« Reply #1 on: June 03, 2019, 05:54:01 PM »
Hi, 

If you download this document, it will explain the whole process:

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

Basically you need a good set of scales and a "rig" so you can weigh the stone in air and in water.  Use the calculation in the document to work out the specific gravity value - it is an excellent non-destructive id test.

cheers
leah
Aussie Sapphire - The Lapidary Warehouse

roughcreations

  • ALF'er Bronze Member
  • *
  • Posts: 16
    • View Profile
    • Email
Re: Specific Gravity test
« Reply #2 on: June 16, 2019, 01:28:02 PM »
Just new at identifying sapphires and was wondering if someone could explain what and how you do a Specific Gravity test thanks.

This is the method I use - e.g. for aquamarine:

Weigh aquamarine: 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!

MALACHI

  • ALF'er VIP
  • *
  • Posts: 709
  • Live long and prospect
    • View Profile
    • Email
Re: Specific Gravity test
« Reply #3 on: June 16, 2019, 02:06:15 PM »
I like the way you have demonstrated the technique. It looks very simple to apply!
Cheers  beers

roughcreations

  • ALF'er Bronze Member
  • *
  • Posts: 16
    • View Profile
    • Email
Re: Specific Gravity test
« Reply #4 on: June 16, 2019, 05:57:14 PM »
Thanks, yes - simple and easy to apply, so encourages one to use the SG value more often as an aid to id. If you are doing the SG reading on a small faceted gem, it is possible to fashion a little sling out of cotton to hold it. The cotton is good as it absorbs water, therefore has little effect on the amount of displaced water. I doubt it would have any effect at all on the second decimal place anyhow, maybe the third or fourth.
RC

Percy1

  • Newbie
  • *
  • Posts: 2
    • View Profile
Re: Specific Gravity test
« Reply #5 on: June 17, 2019, 07:05:39 PM »
Thank you everybody for your help will try some of the techniques you have explained.

Tags:
 

* Sponsor

HTML Online Editor Sample

ALF is hosted by Aussie Sapphire as a free service to the Lapidary community.

Visit our website here
Phone 1800 50 21 40
Or find us on Facebook

Recent Activities

Help with gemmasta and equiment identification by FlashGP
[January 21, 2020, 08:57:16 PM]


facet cutting speed by FlashGP
[January 20, 2020, 07:17:09 PM]


Hey guys I'm in brisbane and looking for a faceting machine for mainly sapphires by FlashGP
[January 20, 2020, 07:15:35 PM]


The old jasper farm coomera by Dihusky
[January 18, 2020, 11:30:35 AM]


Can you refreash laps? by Dihusky
[January 18, 2020, 11:19:58 AM]


Joke of the Day by MALACHI
[January 15, 2020, 05:09:34 PM]


Help How to spot a Fake by steve f
[January 12, 2020, 06:56:36 PM]


Slab Saws are available by Jimnyjerry
[January 12, 2020, 11:51:50 AM]


saw blades...which one to buy??? by Zooti
[January 11, 2020, 08:42:41 PM]


Buying a slab saw by glot
[January 11, 2020, 08:27:08 PM]


Trying to locate a pendulum trim saw. by glot
[January 11, 2020, 08:26:34 PM]


Fires by MakkyBrown
[January 10, 2020, 03:47:46 PM]

* Calendar

January 2020
Sun Mon Tue Wed Thu Fri Sat
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 [22] 23 24 25
26 27 28 29 30 31

No calendar events were found.
Sorry! There are no calendar events available at the moment.

* Who's Online

  • Dot Guests: 69
  • Dot Hidden: 0
  • Dot Users: 0

There aren't any users online.

* Find us on Facebook

* Forum Stats

  • stats Total Members: 4192
  • stats Total Posts: 55251
  • stats Total Topics: 5898
  • stats Total Categories: 6
  • stats Total Boards: 27
  • stats Most Online: 773