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Author Topic: Davis Creek Obsidian, info wanted  (Read 910 times)

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55fossil

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Davis Creek Obsidian, info wanted
« on: May 16, 2017, 07:57:24 PM »

    I just obtained a parcel of Davis Creek Obsidian with great glowing colors... and I do not want to screw it up. The pieces are a bit larger than fist size. Some have definite layers and others just appear as though they are a ball of color with no orientation. So, if someone has cabbed up a bunch of this I would appreciate information on orienting the rough. Do you polish a corner or.......   thanks,  Neal
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bobby1

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Re: Davis Creek Obsidian, info wanted
« Reply #1 on: May 16, 2017, 08:22:42 PM »

I generally look for the color layers and cut parallel to these color layers. I'm always looking for a specific pattern in the layers. If you look closely at the layers you can see a "fibrous-like" pattern. I cut a long narrow high domed cab with these "fibers" going across the narrow dimension. I cut the slabs at least 3/8" thick and usually 1/2" thick. This allows you to cut a steep-sided cab with a high dome. This also makes the cab thick enough to have a nearly black background so there isn't any translucence for the light to shine through. It makes a great catseye cab. I wrote an article for Lapidary Journal in 2011 (I think) showing how to make these cabs. I'm contemplating writing another article on the same subject for Rock and Gem magazine.
 A lot of times you see people suggesting that you cut at 15 degrees to the color layers. This will give you a slab showing multiple colors but it is very directional. If you rotate the piece just a few degrees to either side the color extinguishes.
I have found that by wetting the piece and looking in direct sunlight directly down perpendicular to the color layers you can see the color. If you are in the field hold the piece in your hand facing downward with the color layers parallel to the palm of your hand. Take a small chip off the top of the piece. These chips will expose the color layer(s). A lot of times I have looked through the pile of discarded pieces behind the digging hole and found the piece has been chipped wrong so the color doesn't show. By chipping it right the color pops out at you. I first went to  the site with my dad in the 1980's, though it had been about 4 years since my last visit. 
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rockherder

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Re: Davis Creek Obsidian, info wanted
« Reply #2 on: May 16, 2017, 09:05:52 PM »

I've purchased some rainbow obsidian from a fellow up in Shingletown California.
I asked him how to cut it and he informed me to look for the lines and slice at a 15 degree angle from the lines.
Hope that helps.

Disclaimer:  I haven't cut any of it yet, but I sure like looking at in the sunshine.
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-Doug in El Dorado Hills, CA

55fossil

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Re: Davis Creek Obsidian, info wanted
« Reply #3 on: May 17, 2017, 07:26:30 AM »

   The Cat's Eye does sound like fun. I have read anywhere from 15 to 35 degree angles. I noticed some pieces have many thin layers and others have just one main color with no banding. But that single color glows and changes as you roll the  stone in the sunshine. thanks all, Neal
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lapidaryrough

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Re: Davis Creek Obsidian, info wanted
« Reply #4 on: May 17, 2017, 09:02:18 AM »

http://www.lapidaryrough.com/Slabs.html

  NOT A ADD.....my only host / photos. 

   the slabs are  cut on  the heat band of the cooling phase of the glass.  i use a color pencil an mark the line around the pierce an sq. it up to the blade. so i run the blade through the line i marked.  if the sheen is off a bit i loosen the vise and tap the piece to change degree of cut.

  I do not cut at 15 degree nor 3 degree -  only degree change on sight of first cut. a light tap.

  i use Electra blue sheen to dress my blades...or  220 grit wheel.

  Jack
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Jhon P

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Re: Davis Creek Obsidian, info wanted
« Reply #5 on: May 17, 2017, 09:13:09 AM »

I have cut both ways, a different look on the stone. So try it and see what you like.  The thing I don't like about rainbow obsidian is I needs a bright light best to see the color. Outside jewelry.   I must have a ton of it, I got a commercial permit one time and spent a few days digging.  I have been thinking about cutting a flat and polish it for display specimens
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