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 Post subject: Salvaging Welo Ethiopian Opal from rough
PostPosted: Tue Jul 22, 2014 11:30 am 
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Joined: Sun Jul 20, 2014 2:33 pm
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Here’s some helpful hints for salvaging Welo Ethiopian Opal:
1. In order to salvage the maximum amount of gem quality opal from the smaller cheaper pieces of Welo Opal rough, grind the pieces dry using a hand-held rotary tool fitted with rotary diamond point tips. The opal easily withstands the heat caused by dry-grinding and the diamond tips are not damaged (other than a normal slow wearing of the diamond particles).
• WARNING: Grinding opal dry will create a dust that consists of silica and silica-like matrix. You must wear a dust mast rated to protect you from the type of dust you’re creating and have a ventilation system sufficient to keep the dust away from people and living areas.
2. Do not soak the opal rough prior to grinding and do not use water (or any coolant) during the grinding process. In fact, I highly recommend you do all your initial shaping dry with the rotary tool/diamond tips before your final polishing using the traditional polishing techniques you describe in your article.
3. Before you initiate final shaping and polishing and after you’ve completed your grinding, soak the piece in de-mineralized water the same temperature as your opal (room-temperature). The opal will occasionally fracture, due to invisible fracture lines in the opal and you want this to happen before you put a lot of work into finishing your piece of art.
4. I soaked 510 pieces of salvaged precious Welo Opal. The surface of fifty pieces turned opaque with a chalky appearance. However, every piece regained its resinous luster within a few hours. Although many of the 510 pieces lost their play of color during the one-hour soakings, every one regained that play of color within one hour of being removed from the water and dried off.
5. Drying times for the opal after soaking varies with the humidity and temperature in your area. In Southern Nevada it’s measured in hours. I can see where it could take longer in states like Mississippi or Florida. Use desiccant, humidifiers, and fans if necessary but don’t try to speed drying up by using a hair dryer, microwave, or stove. The sudden heat could shatter the stone.
6. Remove the black coatings found on the “windows” of some of the pieces of Welo Opal (it’s a harmless carbon or manganese coating) using the black Dremel finishing abrasive brush (Package 511E-01). It’s the only one I’ve found so far that removes the coating without scratching the mirror finish on the window. If the black coating is on the matrix or decomposed opal areas just grind it off along with the waste material.

I have absolutely no skill as a lapidary but I find I can easily remove the waste material from a piece of Welo Opal rough in about 20 minutes. The benefit to the true lapidary/artist is the ability to view and appraise the entire piece of opal. Additionally, because so little time is needed to remove the waste material, he or she can salvage a number of pieces quickly and cheaply. Think about the possibilities.

Bob Nolan


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 Post subject: Re: Salvaging Welo Ethiopian Opal from rough
PostPosted: Wed Jan 21, 2015 6:45 pm 
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Joined: Tue May 28, 2013 9:44 pm
Posts: 711
Location: Las Vegas
Bob, your in the Las Vegas area?

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