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 Post subject: Undyed Red Agate
PostPosted: Wed Feb 27, 2013 4:02 am 
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You know I have been wondering a lot about undyed natural red agate. To the best of my knowledge most of the red agate is just greyish white agate dyed to a red color and heated. I have heard that India/Brazil/and too a much lesser extent Yemen still contribute a lot of undyed natural red agate to the market. Is this true? Is it very hard to find natural red agate without it being dyed nowadays? Furthermore since iron oxide is responsible for the red color in the first place, when iron nitrate is used for dying the agates that are so porous how would it be possible to detect anyways? It seems as though this would be the natural ingredient in nature as well. Also when yellow is heated to red, how could that ever be detectable as that could happen in nature as well. Would love to hear your input.


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 Post subject: Re: Undyed Red Agate
PostPosted: Wed Feb 27, 2013 11:05 am 
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 Post subject: Re: Undyed Red Agate
PostPosted: Wed Feb 27, 2013 2:41 pm 
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Having been summoned I'll begin by saying I'm not an expert but I don't believe there's a simple answer. How does jtres define "agate?" It occurs to me s/he may be thinking of carnelian, which is is often mislabled as "agate" but is usually chalcedony. Nearly all carnelian chalcedony I know of is heated in some way, and in some cases possibly dyed using the old German formula of bathing the material in a warm water/iron nitrate solution "as thin as Munich beer" before "burning" it in an oven to achieve the desired hue.

Much of the abundant natural gray fortification agate from Brazil has been dyed and sold as book-ends or wind-chimes in garish, artificial-looking pinks, greens and blues. Many people buy these items thinking the colors are natural and then disappointed when similar colors are not seen in natural un-dyed agates.

Most of the natural red agate I'm aware of occurs as fortification nodules or as jasper-agate combinations in veins. I've seen amazing pure red Mexican Laguna and Coyamito fortification agates, but never in great quantity. I'm sure some natural reds occur in other famous agate deposits around the world.

Iron is an abundant replacement or "feed" component and accounts for many of the red hues in secondary silicated deposits: fossils like dinosaur "bone," horn coral, stromatolites like the famous Mary Ellen "Agate/Jasper" etc., and in primary agate deposits.

Since it's impossible to cover the entire subject in a few paragraphs I'm sure there will be responses taking me to task for omitting this and that. Frankly, the entire subject is not well studied or even defined in terms that are widely accepted. For those interested in this topic I strongly recommend the new book, "Genesis and Classification of Agates and Jaspers: A New Theory" by Marco Campos-Venuti. I think it's available right here on G.O. and it goes a long way in untangling questions like this.

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 Post subject: Re: Undyed Red Agate
PostPosted: Wed Feb 27, 2013 10:16 pm 
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ROM wrote:
Having been summoned I'll begin by saying I'm not an expert but I don't believe there's a simple answer. How does jtres define "agate?" It occurs to me s/he may be thinking of carnelian, which is is often mislabled as "agate" but is usually chalcedony. Nearly all carnelian chalcedony I know of is heated in some way, and in some cases possibly dyed using the old German formula of bathing the material in a warm water/iron nitrate solution "as thin as Munich beer" before "burning" it in an oven to achieve the desired hue.

Much of the abundant natural gray fortification agate from Brazil has been dyed and sold as book-ends or wind-chimes in garish, artificial-looking pinks, greens and blues. Many people buy these items thinking the colors are natural and then disappointed when similar colors are not seen in natural un-dyed agates.

Most of the natural red agate I'm aware of occurs as fortification nodules or as jasper-agate combinations in veins. I've seen amazing pure red Mexican Laguna and Coyamito fortification agates, but never in great quantity. I'm sure some natural reds occur in other famous agate deposits around the world.

Iron is an abundant replacement or "feed" component and accounts for many of the red hues in secondary silicated deposits: fossils like dinosaur "bone," horn coral, stromatolites like the famous Mary Ellen "Agate/Jasper" etc., and in primary agate deposits.

Since it's impossible to cover the entire subject in a few paragraphs I'm sure there will be responses taking me to task for omitting this and that. Frankly, the entire subject is not well studied or even defined in terms that are widely accepted. For those interested in this topic I strongly recommend the new book, "Genesis and Classification of Agates and Jaspers: A New Theory" by Marco Campos-Venuti. I think it's available right here on G.O. and it goes a long way in untangling questions like this.



Thanks so much for the response. In countries in the Middle East where I became interested in agate there is no differentiation in terminology between agate and carnelian. AQEEQ (which translates to agate) is used to describe all forms of chalcedony throughout the region. I have been trying to determine the difference between carnelian and agate and I heard that it is very subjective. I have no education in this however I read somewhere that true carnelian doesn't have bands in it like agate, but has a cloudy dispersion when held up to the light. Needless to say I am quite ignorant about this. I had a stone given to me by a collector that stated that it was a very good quality carbochon aqeeq and it is red (which I thought would be carnelian) but when I held it up to the light I could see some natural parallel lines through the translucent body. I guess there are no easy ways to tell if an agate/carnelian stone has been dyed or heated. I have heard from a geologist that pure red agate does come from India, Brazil, and to a lesser extent Yemen but also heard from this same geologist that visited a famous agate cutting workshop in Iran, that most agates are dyed with the iron nitrate. It would be interesting to know if the Romans or Persians were dying their red agate like that. With all those jewelry artifacts with that beautiful deep red agate, it just seems far-fetched that all of these ancient people would know about some time of iron solution to change the color of the stone to deep red or heat treatment and that it would catch on as a fashion from India to Iran to Greece to Italy. Or that one would take a natural lighter colored stone and just decide to heat it. One would think that at least some had to be natural at some time to get the idea of recreating the dark red color through forms of treatment. I really appreciate all of the help and information ROM.


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 Post subject: Re: Undyed Red Agate
PostPosted: Thu Feb 28, 2013 7:02 am 
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the price for treated and untreated Carnelian is not considerable, because the Enhancement by heat and dying is very common for chalcedonies
but it doesn't mean untreated can not be find

i have some untreated natural rough of Red Quarts and Carnelian

Untreated Red Quartz Rough (kind of brownish red)
Image
Image
Image

Untreated Carnelian Rough
Image
Image

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 Post subject: Re: Undyed Red Agate
PostPosted: Thu Feb 28, 2013 11:44 am 
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When I think of agate, I think of banded material
Image Image

Image

Does red agate occur naturally? Yes.


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 Post subject: Re: Undyed Red Agate
PostPosted: Thu Feb 28, 2013 7:27 pm 
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Those are beautiful fortification agates Barbra.

Cabochon-quality red agate also occurs in vein-type deposits, like the Pigeon Blood Agate (local name) below from a well-known deposit in Utah.

The oval is petrified wood (pseudomorph after wood) from Arizona. While it's commonly called "petrified wood" it might best be described as jasp-agate.


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 Post subject: Undyed Red Agate
PostPosted: Fri Oct 03, 2014 6:21 pm 
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I am not sure if this one goes here but this is an Agate that I found here in North Carolina. Not sure of the type but thought I would share.


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 Post subject: Re: Stone(s) of the Day
PostPosted: Fri Oct 03, 2014 7:04 pm 
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Looks a bit like pink oyster mushrooms lol


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 Post subject: Re: Stone(s) of the Day
PostPosted: Fri Oct 03, 2014 7:46 pm 
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I wish these would grow in my yard like the mushrooms that do! :D


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 Post subject: Re: Undyed Red Agate
PostPosted: Fri Oct 03, 2014 8:36 pm 
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Moved this post to a new area. :D


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 Post subject: Re: Undyed Red Agate
PostPosted: Fri Oct 03, 2014 9:44 pm 
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Thanks Barbra, I am still learning about and exploring this forum. Lot's of fun and I am learning a lot! :D


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 Post subject: Re: Undyed Red Agate
PostPosted: Fri Oct 03, 2014 11:00 pm 
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Wow! I've never seen an agate of that type from NC--we have some yellow seam agates locally here in Raleigh but nothing that nice.
I've found natural carnelian in the field many times. It's not really that rare per se--I would imagine that the issue is that mass-produced jewelry requires large supplies of uniform material, which agate is rarely cooperative in supplying. But the natural material really is nice and does thankfully have some value.

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 Post subject: Re: Undyed Red Agate
PostPosted: Thu Oct 23, 2014 5:17 am 
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I know this is an old post but i did pass around a few samples of red plume agate from Nevada i dug up my self. I unfortunately do not have any samples of it or photo's to post. Barb, if i remember correctly i might have sent you a sample. Possble you can post a photo of it up?

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