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 Post subject: Bytownite/golden labradorite
PostPosted: Sun Nov 18, 2018 5:59 pm 
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Does anyone have any tips on how best to cut this stone? Would it be best to rough a flat on the plane where I can see the sheen and then dop and cut the pavillion? Is it critical to get the plane absolutely correct or do you have a little play?

Some of this stuff is "sleepy" and some of it is clear. Colors range from clear to yellow and pinkish. I'm beginning to wonder if it's really bytownite of if it's sanidine as the SG isn't quite right for bytownite. When I facet it I'll get a RI and maybe that will tell me a little more.

Debbie K


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 Post subject: Re: Bytownite/golden labradorite
PostPosted: Sun Nov 18, 2018 6:43 pm 
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Interesting. I don't think pink would be at all typical for this material. For cutting it it is a pretty cooperative stone. If you want the sheen to be visible in the finished stone put it face up on the table. Being off-axis looks kind of sloppy, though the sheen may align with a cleavage plane making polishing more difficult. Typically bytownite (at least thr Mexican material) shows a silvery sheen that might be something like oriented lilypads, too planar and brilliant to fully resemble moonstone. If you're seeing more of a silvery shimmer that is morw typical of the andesine (sometimes labeled orthoclase) rough that has been around at Tucson for good prices recently.
Anyway, the pink is odd. Probably worth lolishing a flat for an RI reading.

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 Post subject: Re: Bytownite/golden labradorite
PostPosted: Sun Nov 18, 2018 7:11 pm 
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I went through all the feldspar sites I could find looking for anything that mentioned this pinkish color and only the one that I could find was sanidine (and the peachy moonstone), and as it's found in Texas and I am in Texas, that could be what it is. The SG is on target for sanidine, but I'm thinking it's more likely to be golden labradorite, since it's so much more common. The RIs will be different enough to probably be able to tell. Once I get that (and a polished stone or flat) I'll report back.

Debbie K


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 Post subject: Re: Bytownite/golden labradorite
PostPosted: Wed Nov 21, 2018 12:04 am 
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Got some RIs on different facets of the pinky variety:

1.543 -1.554
1.555 - 1.558

SG of 2.65

So, I think it could be andesine. It also is slightly fluorescent under short wave with a yellow/orange glow. The yellow stuff is orange/red under short wave, and the clear is yellowish.

Now that I have one polished, I want to look at the silk under the microscope and see if that's diagnostic. I have a friend that has a Raman; maybe that would help, too.

I'm not posting a picture of the stone as it's horrible. The center is clear and the sides are sleepy. The pink/yellow is not bouncing the way it should. I cut the stone as suggested, but I think that I need to go at right angles to the cleavage planes instead.

If all else fails, I know I can carve it, especially the back of it, and it will look good. Haven't given up on faceting it yet, however.

Debbie K


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 Post subject: Re: Bytownite/golden labradorite
PostPosted: Wed Nov 21, 2018 1:31 am 
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Debbie K wrote:
I have a friend that has a Raman; maybe that would help, too.

It would certainly nail down if it's a feldspar, and it might give a hint on the variety too, though all the feldspars have very similar spectra.
Peach moonstone does certainly exist, and that classic salmon color is a calling-card of potassium feldspar, but I don't think I've ever seen it in a transparent stone. You can get pink in cuprian sunstone from Oregon, though these don't look like that to me.

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