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 Post subject: Ethiopian Welo Opals
PostPosted: Tue Jun 24, 2014 6:50 am 
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Hey Guys! I have found this community to be a great resource with enthusiasts who give honest and straight forward advice. I appreciate in advance you taking the time to help me

I am a novice/hobbyist and have purchased rough Ethiopian Welo opals. The stones I received have beautiful coloring and all I wanted to do was removed the access dirt and drill a hole through the stone to thread a chain through.

I have found that some of the stones are turning an opaque glassy yellow after several wears and was wondering if anybody had any ideas for why this was happening and how I can avoid it - some thoughts I had was that the drill bit is shattering the stone on a micro level or that the heat from the drill bit is damaging the stone....

Is it possible to maintain the rough like qualities of the Ethiopian Welo Opal in relatively rough form without shaping it? Is this something that can be done at home with the right tools? If not, do you have any referrals? Is the stone just to delicate?

Thank you!

-D


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 Post subject: Re: Ethiopian Welo Opals
PostPosted: Wed Jul 02, 2014 9:36 am 
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Location: Washington DC
Hey D,

I've been cutting Ethiopian opals for about five years now and I've seen a couple of different reasons for stones turning yellow and losing color play. A common culprit is oil, these opals will absorb oils from your skin (allthough this usually takes several months of wear) or from any lubricant you're using during cutting. You can soak your stone in acetone for a couple of hours, then let it dry naturally for several days and see if that changes anything.

It could also be humidity, as the stone 'acclimates' to new humidity levels sometimes the appearance changes. I live in DC and I have a couple stones that look very diffferent in the summer than in the winter.

And then there's some mystery stones that seem to maintain their color for several years and then change appearance for unknown (to me) reasons. These are the ones that bother me as a vendor, but I haven't seen too many of them.

I think the cutting proces you're describing is called free form cabbing. You can do it with a rotary tool but it's pretty labor intensive. I've done a couple stones like that with a Dremel but I'm not very good at it and it takes me forever. I send my oddly-shaped rough out to a lapidary I met through Facebook and he does a great job on them with a rotary tool.

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 Post subject: Re: Ethiopian Welo Opals
PostPosted: Wed Jul 02, 2014 10:42 am 
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I purchased 2 Ethiopian opals in Tucson over 2 years ago. They were magnificent then, and they are still magnificent today.


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 Post subject: Re: Ethiopian Welo Opals
PostPosted: Wed Jul 02, 2014 7:13 pm 
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I'm going to guess that the drill was water-cooled. Some Welo opals behave when exposed to water, others don't so well. Sometimes they go cloudy after they dry, a process which can take some time (usually a week for a larger stone in an open container in NC humidity.) That may be what's happened here. Usually stones like that get sorted out in the cutting process, sice they'll be exposed to water then.

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 Post subject: Re: Ethiopian Welo Opals
PostPosted: Tue Jul 22, 2014 5:20 pm 
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You can easily and quickly remove the matrix, decomposed opal, poor opal, and any blemishes by using a rotary tool, diamond rotary tips, and no water (grind dry). There are cheap packages of 15 tips and 30 tips of assorted shapes on the market that result in costs of about 50 cents per tip. I hold the Welo Opals in my bare fingers while grinding with the rotary tool with no problems, other than roughed up finger nails.

WARNING: grinding dry will create dust that's hazardous to breathe, so a properly constructed dust mask and ventilation system is mandatory.


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