July 11-12:BILLINGS, MONTANA: Annual show; Billings Gem and Mineral Club; Sat. 10-5, Sun. 10-4; Free admission!
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Sun Jul 12, 2020 6:41 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 10 posts ] 
Author Message
 Post subject: Heat treating El Dorado Sapphire
PostPosted: Tue Jul 07, 2009 4:50 pm 
Offline
Platinum Member
User avatar

Joined: Wed Apr 26, 2006 12:44 am
Posts: 2051
Location: San Francisco
GIA published an article on the heat treatment of Montana Rock Creek Sapphire, where the author discusses in detail the temperatures and oxidizing/reducing conditions necessary for the Fe oxidation for yellow colored stones, and the reducing conditions/temperatures necessary for reducing the rutile to titanium.

However apparently the one gentlemen who had the skill to treat the el dorado bar montana sapphire has passed away, and so no one seems to know2 how to do that anymore. The GIA article discusses briefly the difference but in no explicit detail.

It would be a real treat if you could discuss the difference and perhaps the temperatures/conditions necessary for the El Dorado material to be heat treated to produce optimum color(s). Since a few of us go up to Montana to the fee-dig sites and collect, we'd really like to be able to get the most out of the big ones we find.

_________________
Custom Gemstone Cutting and various other activities!


Last edited by jleb on Tue Jul 07, 2009 6:03 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Jul 07, 2009 10:36 pm 
Offline
Established Member

Joined: Mon Apr 28, 2008 10:59 am
Posts: 11
Location: Bangkok
Hi Jleb,
I have done many heat treatment experiments on sapphires from Eldorado Bar, Dana's Bar, American's bar and other bars of the Missouri River in the Helena area back in the 1980s. During that time I met many old pros and local miners who tried to heat-treat the Missouri River sapphire. Nobody, including myself, succeeded to heat-treat successfully these sapphires. However, few sapphires have turned to low-quality, somewhat commercially acceptable blue. Note that some of them were contaminated with some types of heat-treatable DryCottonWood Creek sapphires. Full description of the heating parameters are discussed in my book The Heat Treatment of Ruby-Sapphires pages 211-213. Commenting further: The Eldorado sapphires contain very little or no rutile silk. The Fe content is very high. One way to produce blue on Missouri River muddy greenish-bluish sapphires is to create Fe+3/Fe+3 pairs by heating at ultra high temp. in reducing atmosphere (CO2/CO or hydro/nitro). At that time, we used mostly electric furnaces with limited operating temp. to 1700oC, not enough. Gas combustion furnaces were also used (Mr.Dale S.) can go to slightly over 1800oC, but the atmo conditions couldn't be precisely controlled. However, graphite muffle furnace may be used, I didn't had direct access in the 1980s but J.Emmett had, who just had entered the gem treatment field as a hobby and we have collaborated in several projects. As for as a remember I never seen a nice heat-treated Eldorado sapphire, though some exceptions may exist. In the 1990s I attempted again in Thailand heating the Eldorado sapphires with other top-notch experienced Thai treaters without success and we abandoned the project. Wonder, why you don't see Thais pondering in Montana. In 2003 I treated few Eldorado and Dry Cottonwood Creek sapphires with beryllium; the Eldorado sapphires showed signs of color improvement, but of not of acceptable quality; the Dry Cottonwood Creek Rock Creek sapphires were treated with nearly 100% success rate. It is a routine process nowadays. Details of the beryllium process of the Montana sapphires are discussed in my book Beryllium-Treated Rubies & Sapphires. I did not read GIAs article on this issue. I only concentrate on what I actually do myself so I can give you an expert, responsible, and straightforward answer. Hope that helps.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Jul 07, 2009 11:43 pm 
Offline
Platinum Member
User avatar

Joined: Wed Apr 26, 2006 12:44 am
Posts: 2051
Location: San Francisco
Thanks ted, that certainly saved us money and time.. appreciate the answer!

_________________
Custom Gemstone Cutting and various other activities!


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Wed Jul 08, 2009 8:23 pm 
Offline
Established Member

Joined: Mon Apr 28, 2008 10:59 am
Posts: 11
Location: Bangkok
Yes, I lived in Forest Hills-Rego Park. Of course, I remembered Ed Lembeck, one of my best and honest dealers in NYC. I also remembered when I bought my first cubic zirconia from his firm in 1972? (I paid $25/carat those days), together with Marvin working the Ceres (still alive and living in Arizona). I am the same Ted. At the end I didn't rent the space at Lembeck building, I moved to 15 W 47st and thereafter to Broadway + 47th street (my office was behind the famous Coca-cola ad board in Times Square. Are you related to Edward?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Wed Jul 08, 2009 8:34 pm 
Offline
Established Member
User avatar

Joined: Fri Oct 17, 2008 5:11 am
Posts: 45
Location: New York City, Long Island, Syracuse
my grand dad. I managed the company and the building (but not the diamond exchange) and headed up the precious stone department.

you had a mustache correct? I once came to your house and bought a small yellow zircon.

I introduced you to Joe DeCristoforo of Amazon Imports, although I don't expect you to remember him. He remembers you because he was grilling me recently about you. He asked me what the name of the guy was that I had made a big deal about how knowledgeable you were. Imagine that?

You came up to the counter at least once after hours. I once showed you a slice of purple fluorite. Did you know our manger 1972, Al Levine?

The cz was cut right here in NY in those days!

Anyway, good to be in contact with you. I get to Florida about once a year. Orlando area.


Top
 Profile  
Reply with quote  
 Post subject: Re: Heat treating El Dorado Sapphire
PostPosted: Sat Oct 23, 2010 1:37 pm 
Offline
Platinum Member
User avatar

Joined: Wed Apr 26, 2006 12:44 am
Posts: 2051
Location: San Francisco
Well, this topic has come up again. I've bought rough from this guy, and now we are seeing el dorado sapphire heat treated.. I'll see if I can get more information.

http://big-sky-gems.com/facetrough.aspx

Image

_________________
Custom Gemstone Cutting and various other activities!


Top
 Profile  
Reply with quote  
 Post subject: Re: Heat treating El Dorado Sapphire
PostPosted: Sun Oct 24, 2010 5:04 pm 
Offline
Platinum Member
User avatar

Joined: Wed Apr 26, 2006 12:44 am
Posts: 2051
Location: San Francisco
turns out it was old stock, so we still don't know how it was done.

_________________
Custom Gemstone Cutting and various other activities!


Top
 Profile  
Reply with quote  
 Post subject: Re: Heat treating El Dorado Sapphire
PostPosted: Sun Oct 24, 2010 5:36 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Sat Jul 11, 2009 10:29 am
Posts: 928
Location: USA
http://gemmountainmt.com/default.aspx

_________________
http://www.gemaddicts.com <--- My Website
http://www.gemsbyjennifer.com/store <---- Wifey's Store
http://www.flickr.com/photos/digitaldevo <--- My Portfolio


Top
 Profile  
Reply with quote  
 Post subject: Re: Heat treating El Dorado Sapphire
PostPosted: Mon Oct 25, 2010 1:23 am 
Offline
Platinum Member
User avatar

Joined: Wed Apr 26, 2006 12:44 am
Posts: 2051
Location: San Francisco
swish, Heat treating rock creek isn't the problem.. it's the el dorado bar stuff (from a different local) that is the question.

_________________
Custom Gemstone Cutting and various other activities!


Top
 Profile  
Reply with quote  
 Post subject: Re: Heat treating El Dorado Sapphire
PostPosted: Mon Oct 25, 2010 6:08 pm 
Offline
Gemology Online Veteran
User avatar

Joined: Sat Jul 11, 2009 10:29 am
Posts: 928
Location: USA
I realize this, and know they react totally different due to differing compositions, I just figured it may at least give a bit more info for a possible starting point, that was all.

_________________
http://www.gemaddicts.com <--- My Website
http://www.gemsbyjennifer.com/store <---- Wifey's Store
http://www.flickr.com/photos/digitaldevo <--- My Portfolio


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock