Weld retip on an opal 

Please DO NOT weld near an opal unless you are completely confident that you will not harm it.
I am showing you how I retipped an opal so that you can see the capabilities of using the welder when you have the experience to know exactly how close you can get the weld to a sensitive stone without harming it. This comes from experience and careful thought before you start welding.
On this job I had to do a full retip (20 tips) but one of the opals was already cracked, which meant I could not take it out. I therefore decided to retip it with the opals in.
To avoid harming the opals, I did the following :
Snipped the claw at an angle below the edge of the opal to keep the weld easy to access with the electrode but far enough away from the opal for safety
Made the end of the tipping wire square to shield the opal from the blast of the weld.
Used 30% power to weld the tip on, far enough away from the opal, so that it welded cleanly first attempt to avoid risky re-welding
Used 25% power to then build up the base/side of the claw for strength, all the time holding the feeder wire between the weld and the opal (this acts as a shield)
Generally stayed in control of my actions and showed extreme caution, opals will harm very easily
This was done on the Lampert PUK 3S on the GAP setting (I usually use STANDARD for retipping). The strength of each weld on the PUK is dependably consistent with little variation so I can predict and plan the welding near sensitive stones. If you want to weld near stones like this please practice first on old stones !