doublet83
starting to spend too much on rocks
Member since March 2016
Posts: 118
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Post by doublet83 on Aug 13, 2016 11:50:33 GMT -5
www.ebay.com/itm/121870882389?_trksid=p2057872.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AITRecently bought this pair of neat looking dark brown agate bookends. I don't think they are dyed, because of the distinct color between the bands, especially the brown and white bands, along with the quartz, which didn't have any brown coloring. But I'm still a novice at determining this sort of thing. Wondering what others think? I assume these are Brazilian agate but not 100% on that either.
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dottyt
spending too much on rocks
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Post by dottyt on Aug 13, 2016 12:29:41 GMT -5
I can't tell you if yours are dyed or not, but it is most definitely possible to dye agates so that the bands are very clear. Perhaps someone else can say if this is the way they dye automatically, because the layers of the stone absorb the dye differently or whatever. Here's a photo of different colors that can be used (I hope): www.minerals.net/mineral/agate.aspx?img=/Image/13/171/Agate.aspx
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Post by jakesrocks on Aug 13, 2016 14:00:19 GMT -5
My guess is that they are natural. It would be nearly impossible to dye them without the matrix also being dyed.
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doublet83
starting to spend too much on rocks
Member since March 2016
Posts: 118
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Post by doublet83 on Aug 13, 2016 14:12:12 GMT -5
I've seen some dye jobs where the bands absorb the dye differently, thus retaining some of the distinct banding, but the coloring does tend to spill over to everything in a somewhat inconsistent manner. In this case, the browns are consistently brown throughout, and whites are bright white with no hint of brown, and the quartz also does not have a hint of brown.
Also, I've seen some dark brown color naturally occurring in Brazilian agate before, although not to this extent.
I do have limited experience, and this could just be a much better dye job than what I've seen before,
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Post by vegasjames on Aug 13, 2016 14:24:39 GMT -5
With the various shades it looks natural to me. You can try rubbing a cotton swab dipped in acetone over some of the areas to see if there is any dye.
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Thunder69
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Post by Thunder69 on Aug 13, 2016 19:13:42 GMT -5
I would say that they are natural...Nice deal too...John
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doublet83
starting to spend too much on rocks
Member since March 2016
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Post by doublet83 on Aug 14, 2016 13:18:23 GMT -5
Thanks for the replies. I'm glad others feel they are natural as well. Always wonder with these bookends..
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Deleted
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Post by Deleted on Aug 14, 2016 16:13:08 GMT -5
I'm going to offer a different opinion - dyed - just because brown is one of the colors that Brazilian material gets routinely dyed to up the contrast in the banding of an otherwise fairly drab gray agate. That certainly is an attractive pair, dyed or not, and not garish at all. Brazilian dyers (as with their German mentors) do a very good job of selecting stones that will dye well. The stone must have banding of varying porosity so that some bands take up color, while others do not. Some of the Brazilian geode material contains layers that allow dye penetration much farther into the stone than most I've seen. In the bookend geodes that I've seen, few have matrix/rind where the dye penetrates (I'm thinking just a brush with cutting oil keeps the dye from taking). I've even seen some where more than one color dye has been used, including this one, which was dyed an obviously artificial blue and green (not shown in the photo) with no spreading of the dye into the matrix. I think it would be fascinating to visit one of these outfits to watch what goes on - I have a hard time imagining the techniques are used for the multi-color pieces - I expect it involves some sort of resist coating to block certain areas, but it would still require a good grasp of the particular material to prevent bleeding/mixing.
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doublet83
starting to spend too much on rocks
Member since March 2016
Posts: 118
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Post by doublet83 on Aug 14, 2016 19:32:17 GMT -5
I'm going to offer a different opinion - dyed - just because brown is one of the colors that Brazilian material gets routinely dyed to up the contrast in the banding of an otherwise fairly drab gray agate. That certainly is an attractive pair, dyed or not, and not garish at all. Brazilian dyers (as with their German mentors) do a very good job of selecting stones that will dye well. The stone must have banding of varying porosity so that some bands take up color, while others do not. Some of the Brazilian geode material contains layers that allow dye penetration much farther into the stone than most I've seen. In the bookend geodes that I've seen, few have matrix/rind where the dye penetrates (I'm thinking just a brush with cutting oil keeps the dye from taking). I've even seen some where more than one color dye has been used, including this one, which was dyed an obviously artificial blue and green (not shown in the photo) with no spreading of the dye into the matrix. I think it would be fascinating to visit one of these outfits to watch what goes on - I have a hard time imagining the techniques are used for the multi-color pieces - I expect it involves some sort of resist coating to block certain areas, but it would still require a good grasp of the particular material to prevent bleeding/mixing. Thanks for your opinion. Do you think its dyed because you think the dark brown color is unnatural looking? Are there any other factors that look suspicious to you?
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Deleted
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Post by Deleted on Aug 15, 2016 4:36:35 GMT -5
Thanks for your opinion. Do you think its dyed because you think the dark brown color is unnatural looking? Are there any other factors that look suspicious to you? My first thought when I come across Brazilian geodes like this is to look for dye, simply because they don't come with much of any color (unless there is some new discovery). Agate dyeing is done on an industrial scale there, as elsewhere, and the rind and solid crystal interior interspersed with banding are both identical to the interiors of the geodes used for dyeing. The brown color closely resembles sard, which is often dyed these days even when it comes from elsewhere. In the picture of the unmatched bottom of the pair, you can see what looks like some "leakage" of color into and between the quartz crystals. You can try rubbing hard on an inconspicuous place with a white cloth soaked in acetone to detect some dyes (don't do it where you can see, as it can leave a ring or light spot), but even that won't show any result for some dye processes used these days. Better to put it under a microscope and look for accumulations of dye in cracks and weak spots inside the stone, seepage, pooling, etc. - I'd concentrate on that suspicious area on the bottom of the pair. As I said, yours is less obvious than the gaudy colors one sees in gift shops and is quite attractive.
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