Post subject: Seperating Saltwater and Freshwater Pearls
Posted: Tue May 08, 2012 4:20 am
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Tip from Dr. Henry Hanni: To test a pearl to determine if it is fresh or salt water (which has become more difficult as the Chinese Freshwater are getting more sophisticated), we can rely on the additional manganese all freshwater pearls contain. The manganese content of freshwater pearls is 3X greater than salt water.
Using Manganese test strips (inexpensively available online) and some diluted hydrochloric acid we can test for Mn content.
As I understand it, we drop a wee amount of diluted hydrochloric on the pearl. According to Dr. Hanni, the pearl will not be damaged. Swipe the Mn Test strip over the area and if it tests positive for Mn, you have a freshwater pearl.
Our member Earthling, aka Oliver said he would do a little further research and testing on this and report back.
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Tue May 08, 2012 5:50 am
Valued Contributor
Joined: Sat Oct 13, 2007 9:03 am Posts: 109 Location: Italy
Wow! thank you Barbra for this tip! How many part per milion (ppm) of concentration of the strips test it will be used? And the concentration of HCL? 10%?
Bye Paolino
_________________ Paolo Cerruti G.G. (GIA)
"When the winds of change blow, some people build walls and others build windmills" www.paolocerruti.it
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Tue May 08, 2012 11:16 am
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Earthling should be back home and settled shortly. I'm sure we'll hear back. We both heard the PEARL lecture by Dr. Hanni at the Scottish Gemmological Conference. He spoke of the test rather quickly, like we'd all just "get it".
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Wed May 09, 2012 3:35 pm
Valued Contributor
Joined: Tue Oct 17, 2006 11:33 am Posts: 403 Location: New Zealand
Hi
the solution used is HCL 10%, the test will just indicate the type of pearl if it will show color on the stripe to one of the ends, either minimum or maximum level. Everything in between will not be diagnostic since it could be a freshwater pearl that was grown in an estruary with saltwater content and therefore the mangan level would be higher. I will order one of the tests and give it a go to work and report back.
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Wed May 09, 2012 4:02 pm
Gold Member
Joined: Sun Jun 28, 2009 9:56 am Posts: 1284
10% HCl sounds quite aggressive. What about something softer such as white vinegar?
Note that a little bit of remaining acidity can be harmful with time (especially in a porous material which will retain traces of acid in the pores). Here's what people usually do with minerals after acid has been added: first they thoroughly rince the sample with water, and then they proceed to neutralisation by soaking it in a saturated solution of sodium bicarbonate, and then they rince it again with distilled water. I would suggest training on some value-less samples first.
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Wed May 09, 2012 4:12 pm
Valued Contributor
Joined: Tue Oct 17, 2006 11:33 am Posts: 403 Location: New Zealand
The test will be sure to some degree a destructive one, but as said this is just something that is still in its baby-shoes and have to be developed until it can be used properly.
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Thu May 10, 2012 10:00 am
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
What we need to do, is a little experimentation with some "crap" pearls to check on the reliability of the process and whether or not we can detect any damage to our test pearls.
Post subject: Re: Seperating Saltwater and Freshwater Pearls
Posted: Thu May 10, 2012 11:11 am
Gemology Online Royal Princess
Joined: Mon Oct 17, 2005 10:56 am Posts: 6461 Location: The frozen north prairie :-/
Boy! Have I got a "crap" pearl for you . It's a FW pearl that developed at the shell and shows the insides on a couple of "sides" of the pearl. Let me know if you'd like a photo and if it could be of service .
_________________ IIJA Registered Gemologist GIA Graduate Gemologist
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