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[ileney]

I bought these small tumbled agates (1.5" by about 1.5 to 2") on ebay for very little. They were listed as all natural Madagascar banded agate, but the dark stripes and white bands seem almost too much of a contrast to the orangish body to be natural. They certainly feel like agate and otherwise look like it. I was thinking of slicing them to make small cabs because the bands are so striking, but am wondering if there are any opinions if 1) this is really from Madagascar 2) it is really undyed (if not, perhaps the color will not be present very deep) and 3) if there is a particular name for this. Here are a couple of images of them below.

[Ranger_Dave]

I'm thinking natural. Most of the dyed stuff I've seen is often some bright, garish, color. I have seen natural banded agates that look like what you have.

[southerly]

does not look dyed but could be heat treated to darken the colours

[jakesrocks]

Madagascar has produced natural agates like yours. Check these pics. https://www.google.com/search?q=madagascar+agates&safe=strict&biw=1600&bih=764&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiOlomQ44XSAhXM1IMKHcayDJkQsAQIGQ#imgrc=BJg0v2OXtxzlrM:

There was also a treatment used years ago where agates were cooked in an acid solution to produce brown banding in otherwise colorless agates.

I believe yours are natural.

[rocks2dust]

There was also a treatment used years ago where agates were cooked in an acid solution to produce brown banding in otherwise colorless agates.

You are correct, and the sugar-acid treatment is still very widely used - cheap and no expensive technology or chemicals needed. Boiling with iron nitrate is another easy method to get red-brown and red, and there is quite a bit of color-enhanced Madagascan agate that gets used in the bead and cheap cabochon trade. The color can penetrate fairly deeply into agate, so best to go over a piece using a microscope looking for flecks of colorant clumping together, puddling and bleeding into fissures and weak/more porous spots within the stones to detect ID dyes and similar color enhancements. Although the day-glo dyes are obvious, it is almost impossible to tell the more subtle treatments from just a photo.

[ileney]

Thank you for all the information folks. Looks like I'll find out for sure when I cab one of them and see if the dark color penetrates all the way to the center of the stone.

[agatizer999]

Dear ileney,

I just purchased the same stones as you got here. I bought it in an online store, who most probably got the "Madagascar agate" from a Chinese source. After receiving them I suspected that they had been dyed. They have dark strikingly visible but not uniformed stripes, which form broken lines and there are small blots here and there, plus white bands and red and orange body, very very much like what you got there in the picture. I'm wondering if you found yours dyed when you sliced it up to make small cabs. I wish to know because my stones have been polished shiny and I don't intend to cut it into smaller pieces. Thank you in advance for your response, it would be priceless to me!

[lithicbeads]

A number of years ago before the 2008 bust it was reported that bubblegum coloration chemicals were used to color agates in china .The Germans are the ones who started using aniline dyes on agate and it seems never to end.

[Eddie P]

I have quite a few of these and although I have never cut through one I am quite certain they have been treated. It's worth comparing them to the many photos of untreated red/orange/pinkish American agates available the web e.g. the dryheads from Montana.  The colours here are too dark and too rich, the intense red/black contrast not replicated on any natural agate that I have seen from a reputable source. Could that much iron-staining get naturally into an agate?  It would be amazing and they'd be highly sought after. Yet the cheap price reflects the fact that it's actually very easy to change colour from grey/pale orange as described above.

[Felicia]

Looks to me like it's not dyed. Nice banding, good looking stones.

[Shifter55]

These are definitely dyed, the white banding is a characteristic tell for me, but after tests with some similar tumbles last year I think the dye only penetrates the first millimeter of the stone. The black seems to go further but you end up with intensely patterned white/grey agate.

Could that much iron-staining get naturally into an agate?

I'll attach an image of natural iron staining for you, it's yellow limonite rather than anything red, and cutting tends to be a bit smelly.

[irockhound]

They look dyed to me.   The 2nd pic with the splotchy color and what looks like areas that were more receptive of the dye.  We will see when they are cut.  I just did a search after posting and there has been someone who cut one to check for a dye process.  It is from the Journal of Gemmology, London

https://search.proquest.com/openview/6f1bf64b14b92d0fb9e41c7c959cce6c/1?pq-origsite=gscholar&cbl=2041200

Shoot, After I posted the link I followed the link and now it says I must log in through a library to view where before it let me read the article.  It said basically that they cut one to test it and found that the coloration only existed in the outer rind and the inner agate was just a White banded Agate.  It also stated that the more translucent layers had the dye penetrate a bit more.  I tried going to the next page to show the cut sample and not I am blocked without the library access..  I'll try clearing my internet cache and see if that will let me see it again.  After clearing the cache I was able to get back to the first page of the article.

[ileney]

Sorry. I somehow forgot to come back here and post. Yes, they are dyed.