Sabre52
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Post by Sabre52 on Jan 12, 2015 10:42:57 GMT -5
Howdy folks, Found this when I was sorting Rio Grande agate yesterday. This chert is not usually this color. Looks almost like it has been heat treated because this is the color it turns if heated. Clayton tells me there are lots of Amerind mounds in the agate beds so this may very well have been utilized by native Americans.....Mel  |
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jamesp
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Post by jamesp on Jan 12, 2015 11:12:07 GMT -5
Sometimes the heated material will have pock marks in it Mel. If it chips real smooth there is a good chance it is heated. Likely was yellow before if heated.
Palm looks that color after heat, starting yellow/beige. If it is natural red, wow.
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Sabre52
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Post by Sabre52 on Jan 12, 2015 13:48:28 GMT -5
James: Yeah, our local flint and chert runs mainly light to dark cocoa brown but turns more red if heated.....Mel
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jamesp
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Post by jamesp on Jan 12, 2015 15:03:14 GMT -5
James: Yeah, our local flint and chert runs mainly light to dark cocoa brown but turns more red if heated.....Mel Common colors in our coastal plain chert. Fossiliferous silicifications do nice color changes. The ones formed from minerals leaching from limestone. Why is that ? Of all the rocks I treat, the coral and the coastal cherts really get color changes. I know, it is a serious chemistry question and probably very complicated for that reason. |
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Sabre52
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Me and my gal, Rosie
Member since August 2005
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Post by Sabre52 on Jan 12, 2015 19:37:47 GMT -5
Dunno for sure. Maybe the heat causes oxidation of included iron salts causing the red tones......Mel
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jamesp
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Post by jamesp on Jan 12, 2015 20:00:30 GMT -5
Dunno for sure. Maybe the heat causes oxidation of included iron salts causing the red tones......Mel Like moss agate is bad about turning brown. May help to use a lower temp on them. |
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Fossilman
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Post by Fossilman on Jan 12, 2015 21:36:40 GMT -5
Nice!
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Post by snowmom on Jan 13, 2015 6:01:03 GMT -5
pretty pretty!
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tkvancil
fully equipped rock polisher
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Post by tkvancil on Jan 13, 2015 10:34:26 GMT -5
That's really cool. We have a good amount of chert here in Illinois. Many have crinoids and other fossils. My favorite local rock to tumble.
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Deleted
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Post by Deleted on Jan 17, 2015 18:59:33 GMT -5
James: Yeah, our local flint and chert runs mainly light to dark cocoa brown but turns more red if heated.....Mel Common colors in our coastal plain chert. Fossiliferous silicifications do nice color changes. The ones formed from minerals leaching from limestone. Why is that ? Of all the rocks I treat, the coral and the coastal cherts really get color changes. I know, it is a serious chemistry question and probably very complicated for that reason. Heating adds energy. That energy can be used to form new bonds, or break them. Using the salts and ions present, ad heat and you may oxidize (or reduce) the salts and a color change will happen. One famous color change with heat is amethyst to citrine. Gem select tells us When it says "iron impurities are reduced" they don't mean lessoned. Instead it means chemically reduced (oxygen released). For instance Yellow Iron Oxide Hydroxide (FeOOH = Goethite). Heat that and you get red Iron Oxide and water 2FeOOH + Heat = Fe 2O 3 + H2O |
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Deleted
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Post by Deleted on Jan 17, 2015 18:59:49 GMT -5
I am pretty sure my stoichiometry is correct.
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jamesp
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Post by jamesp on Jan 17, 2015 21:53:22 GMT -5
Take it easy Scott, just a dumb redneck here. It is a reaction and not easily described w/out such terminology. understood
But I do get the gist and appreciate the answer.
I know they heat those amethyst cathedrals found in Brazil and convert them to citrine.
And pretty sure iron is a major coloring agent in our beloved stones.
I think heating is practiced on gemstones commonly.
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Deleted
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Post by Deleted on Jan 17, 2015 22:43:53 GMT -5
Take it easy Scott, just a dumb redneck here. It is a reaction and not easily described w/out such terminology. You are no dummy. I know you far better than that. You just play a dummy on TV!  If you look at my chemistry equation: Iron Oxide Hydroxide + heat = Iron Oxide + water (in words) is the same as 2FeOOH + Heat = Fe2O3 + H2O (in symbols) 2FeOOH is: 2 Iron atoms (Fe is iron) 4 Oxygen atoms (O is oxygen) and 2 Hydrogen (H is hydrogen) heat that up and the energy re-arranges the atoms Fe 20 3 - Iron Oxide is formed H 2O - water is also formed If you add up the atoms before and after the heat I have the same number of each element. But new compounds have been formed with them. Very discrete. I am NOT a chemist (anymore) and I do not play one on TV. |
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jamesp
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Post by jamesp on Jan 18, 2015 4:36:45 GMT -5
Take it easy Scott, just a dumb redneck here. It is a reaction and not easily described w/out such terminology. You are no dummy. I know you far better than that. You just play a dummy on TV! If you look at my chemistry equation: Iron Oxide Hydroxide + heat = Iron Oxide + water (in words) is the same as 2FeOOH + Heat = Fe2O3 + H2O (in symbols) 2FeOOH is: 2 Iron atoms (Fe is iron) 4 Oxygen atoms (O is oxygen) and 2 Hydrogen (H is hydrogen) heat that up and the energy re-arranges the atoms Fe 20 3 - Iron Oxide is formed H 2O - water is also formed If you add up the atoms before and after the heat I have the same number of each element. But new compounds have been formed with them. Very discrete. I am NOT a chemist (anymore) and I do not play one on TV. You spelled it out well. I would not get that on my own. Ha, chemistry kicks my tail. My strong suit would be cooking agates/silicates and knowing whether or not it needs more or less heat. and that by judging color change and effects on mechanical properties. Chemistry-ha no way. I read about the composition of Savannah River agate and the colors it turns from a mix of components. It stepped over my head in a hurry. |
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