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 Post subject: Chatoyant Serpentine?
PostPosted: Wed Oct 11, 2006 10:10 am 
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During one of our trips to visit family in Delaware, we were wandering a state park and I noticed green serpentine in some roadfill along a path. Serpentine is native to DE, so that wasn't too surprising -- what made me curious was the fact that the serpentine was nicely translucent and has a definite fiberous structure. Here are a couple pics of a decent piece:

Image (no flash)
Image (with flash)

I've read about, but never seen, chatoyant serpentine. I'm not a cab cutter (maybe someday), so I don't know how to evaluate rough for chatoyancy.

I'm fairly certain this material is solid enough for cabbing -- can anyone clue me in on how to determine if it will have an eye?

peter

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PostPosted: Wed Oct 11, 2006 11:11 am 
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Cat's eyes is the result of needle like inclusions, mineral needles or growth channels, hosted in a mineral body, which reflects light up to the viewer. E.g. crocidolite or rutile inclusions in quarts or growth channels in tourmaline. I haven't read anything on it, but my experience is that pure, fibrous materials won't give cat's eyes because they are too densely packed, there is no space for the light to scatter and the light is therefore reflected right up from the surface like on a usual cab. If you sand them on a rough wheel and then go straight to polish, you can get some effect, but on the cost of the surface polish. It works for common eye-stones and star stones too, it is not uncommon to improve a weak star corundum in this fashion.

I've seen small serpentine cat's eyes from Arizona which showed simply amazingly bright eyes, where the effect was ascribed chrysotile inclusions. The easiest way to see if there'll be an eye is to polish a small face at 45 deggrees on the edge, then you see if it is the material itself which is fibrous, or if it is inclusions which causes the silky sheen. A fibrous material goes dead dull.

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 Post subject: Re: Chatoyant Serpentine?
PostPosted: Wed Oct 11, 2006 12:58 pm 
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pt wrote:
I'm fairly certain this material is solid enough for cabbing -- can anyone clue me in on how to determine if it will have an eye?

Serpentine is soft so you should be able to sand a small flat spot by hand using carborundum paper: 200 grit to 400 or so. Then put a single drop of high-viscosity oil like STP on the sanded area. It will "bead up" and you should be able to see the eye if any. It works on star stones so I don't know why it won't work for cat's-eyes too.

Rick Martin


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 Post subject: Re: Chatoyant Serpentine?
PostPosted: Wed Oct 11, 2006 2:23 pm 
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ROM wrote:
Serpentine is soft so you should be able to sand a small flat spot by hand using carborundum paper: 200 grit to 400 or so. Then put a single drop of high-viscosity oil like STP on the sanded area. It will "bead up" and you should be able to see the eye if any. It works on star stones so I don't know why it won't work for cat's-eyes too.


Excellent -- the kids were itching to get outside anyhow. I'm gonna go play with rocks!

peter

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PostPosted: Wed Oct 11, 2006 3:12 pm 
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Chrysotile is a form of asbestos, right? So it might be a good idea to wet sand the stuff and not go huffing the dust...

Might it also be tremolite, not serpentine?

Up here in the frozen north we find "catseye jade" which is apparently chatoyant actinolite.

Hardness is the rough-and-ready test to separate the serpentines (Magnesium) from tremolite-nephrite-actinolite(Calcium)? Call it serpentine if it's soft?

Wishing I were more of a mineralogist,
Chris


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PostPosted: Wed Oct 11, 2006 3:46 pm 
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I can't tell you whether it will cut with an eye en cabochon; however I don't think this occurrence is that unusual. To my knowledge it is quite common in serpentine. I have seen and found many pieces on the isle of Unst, Shetland. I believe that the fibrous nature is due to the presence of a form of asbestos which has been serpentinised.

Peter Hurst


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PostPosted: Wed Oct 11, 2006 4:40 pm 
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This looks pretty similar to your piece:

http://www.minerals.net/mineral/silicat ... rpent2.htm

Again, though the risk is probably miniscule, I don't think I'd go dry sanding chrysotile.

Staying tuned,
Chris


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PostPosted: Wed Oct 11, 2006 5:50 pm 
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It's soft stuff -- 100 then 220 sandpaper quickly gives it a nice waxy look. I took the risk on dry sanding, but then it's a windy day here and I was working outside. I doubt I sucked down much if any. I'll post a pic later since people seem interested.

It's got a definite sheen, but I haven't been able to try ROM's test. I thought I had some high-viscosity oil, but...

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PostPosted: Wed Oct 11, 2006 5:59 pm 
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beadiste wrote:
Again, though the risk is probably miniscule, I don't think I'd go dry sanding chrysotile.

Staying tuned,
Chris

Chris, I think "miniscule" is the operative word here. Since I'm the evildoer who suggested the brief sanding operation, I did a little searching on the topic. Here's what I found:

"Data suggest that amphiboles are the major cause of mesotheliomas in asbestos workers." On the basis of medical studies, "amphiboles are more potent than chrysotile in the induction of fibrotic lung disease and associated lung cancer."

The reason for the difference in virulence is that "rod-like amphiboles appear to penetrate the peripheral lung more readily than chrysotile fibers, which are curly" (Mossman 1990, pp. 294-295). Furthermore, according to the Stanton hypothesis, "fibers longer than 8 m and less than 0.25 m in diameter have the most marked carcinogenic potential." This is presumably a result of the differing shapes, which means that "chrysotile fibers, in comparison to amphibole fibers, are cleared more readily from human lungs."

"The available experimental and epidemiological data indicate that both fiber types are important determinants of the pathogenicity of asbestos." <b> "Recent epidemiological data are concordant with the suggestion that exposure to chrysotile at current occupational standards does not increase the risk of asbestos-associated diseases." </b>However, "federal policy in the United States does not differentiate between different types of asbestos."

"This makes little sense, since, "with few exceptions, the type of asbestos fiber found predominantly in buildings is chrysotile." (Mossman, p. 247). Furthermore, removal will cost $53 billion, but estimates range up to $100-150 billion (Mossman 1990, p. 94). "Recent epidemiological studies of deaths from mesothelioma in the general population also suggest that risk from asbestos in buildings is minuscule."

Risks of asbestos-related total deaths (both lung cancers and mesothelioma) due to exposure in schools are magnitudes lower than commonplace risks in modern day society," for example, 0.005-0.096 deaths/million compared to 6 deaths/million for airplane accidents. "The available data and comparative risk assessments indicate that chrysotile asbestos, the type of fiber found predominantly in U. S. schools and buildings, is not a health risk in the nonoccupational environment. Clearly, the asbestos panic in the U. S. must be curtailed" (Mossman 1990, p. 299)...

Ross comes to similar conclusions about the health risks associated with cancer. "Pleural cancer seems to be caused by crocidolite asbestos but not by chrysotile or anthophyllite asbestos. <b>Lung cancer is caused by chrysotile, anthophyllite, amosite, and crocidolite asbestos in asbestos workers who smoke cigarettes. Evidence for excess lung cancer in nonsmoking asbestos workers is weak. Two completely different substances, asbestos and cigarette smoke, combine to produce a very significant risk to many asbestos workers, particularly those who are heavily exposed to asbestos dusts." </b>

<b>"Generally, asbestos related diseases appear in asbestos workers only after many years have elapsed since first exposure. A significant increase in the lung cancer death rate appears 10 to 14 years after first exposure and peaks at 30 to 35 years. The mesothelioma death rate becomes significant 20 years after the first exposure, but continues to climb even after 45 years have elapsed. The asbestosis death rate becomes significant 15 to 20 years after first exposure and apparently peaks at 40 to 45 years" (Ross 1981, p. 303). </b>

<i>Source: http://scienceworld.wolfram.com/chemistry/Asbestos.html</i>

Rick Martin


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PostPosted: Wed Oct 11, 2006 7:17 pm 
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pt wrote:
It's soft stuff -- 100 then 220 sandpaper quickly gives it a nice waxy look. I took the risk on dry sanding, but then it's a windy day here and I was working outside. I doubt I sucked down much if any. I'll post a pic later since people seem interested.

It's got a definite sheen, but I haven't been able to try ROM's test. I thought I had some high-viscosity oil, but...


Sounds nice, look forward for the pic! I don't think you have to worry that much about the dust if you did it outside.

agatepete wrote:
I can't tell you whether it will cut with an eye en cabochon; however I don't think this occurrence is that unusual. To my knowledge it is quite common in serpentine. I have seen and found many pieces on the isle of Unst, Shetland. I believe that the fibrous nature is due to the presence of a form of asbestos which has been serpentinised.

Peter Hurst


I agree with you, it is probably not very unsual, considering how common serpentine is, and I have seen larger, emerald green examples from Norther Norway too, although not with as good effect as in those from Arizona, but it is rarely seen in the market. At least around here, which maybe don't say so much since Swedens sucks when it comes to gems.

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PostPosted: Wed Oct 11, 2006 11:09 pm 
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Thanks, Rick!

Locally we had a tremolite scare last summer when some lab determined that the rock being crushed from a local quarry was laced with tremolite. Needless to say this was disturbing to the guys on local construction crews who wondered how much of the stuff they'd been exposed to over the years. Then there was the asbestos mine served by the Skagway railway - I remember my son returning from a scouting trip with the coins flattened on the rails by the freight cars full of asbestos...
and our local schools that had to have asbestos removal measures taken... So it's a relief to read something for a change that puts the mesothelioma risk in perspective.

Best regards,
Chris


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PostPosted: Thu Oct 12, 2006 9:10 am 
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Jung Kee wrote:
I agree with you, it is probably not very unsual, considering how common serpentine is, and I have seen larger, emerald green examples from Norther Norway too, although not with as good effect as in those from Arizona, but it is rarely seen in the market. At least around here, which maybe don't say so much since Swedens sucks when it comes to gems.


It's pretty much the same here in Indiana. Gems are non-existent in the US Midwest -- unless you can facet calcite, you're pretty much outta luck. Even our quartz doesn't usually get big enough to facet. A couple states to the west has some fluorite, but that's about it AFAIK.

That's why something as common as serpentine makes my day when I find it -- if it is a gem material, all the better.

Ironincally, there are gold, diamond and sapphire finds here in Indiana, certainly from glacial deposits. I've only read about it in old books, and have not heard of anyone finding anything in the past 50 years or so -- except for the few grams of gold which some hard-core hobbiests eek out of our streams every year.

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PostPosted: Thu Oct 12, 2006 9:54 am 
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Here is the little piece I played with yesterday. I chose a different piece b/c I rather like the first one above as a specimen.

Image
Image

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