ZackAttack
starting to shine!
Member since January 2007
Posts: 45
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Post by ZackAttack on Oct 12, 2006 21:31:24 GMT -5
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Post by gemkoi on Oct 12, 2006 22:03:50 GMT -5
Onyx from Mexico
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,456
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Post by Sabre52 on Oct 12, 2006 22:04:37 GMT -5
Looks like travertine. If it is it should easily scratch with a knife as traverine is basically a fairly soft material made of calcite or aragonite...mel
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Post by ladyt on Oct 13, 2006 11:41:49 GMT -5
Yes It is travertine. I slabbed a larger one and shared the pieces. I tumbled some and it tumbles great. Kinda soft so watch it closely. I have some waiting for the pre-polish stage. Tonja
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spacegold
has rocks in the head
Member since September 2006
Posts: 732
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Post by spacegold on Oct 14, 2006 14:44:40 GMT -5
If it is really hard, it would be agate.
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Post by gemkoi on Oct 17, 2006 12:46:01 GMT -5
IM sorry, but I disagree 100% as it being travertine. Seen thousands of pounds of this stuff for years label as Mexican onyx. As well as finished plates, bowls, chess sets, and many other trinkets. Travertine will have lots of inconsistency, because it water rock, grows very fast in high mineral rich waters. Here in Arizona there’s a place called "fossil creek", and each year you can see how the travertine builds up barriers, and then a flash flood breaks it all down. Highly porous stuff too. Its what is so trendy in homes for tile work now adays. Plus travertine wont be translucent as that piece looks to be.
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,456
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Post by Sabre52 on Oct 17, 2006 14:03:37 GMT -5
Shain: I think if you check, all Mexican "Onyx" is a form of travertine. It is a calcite-marble type material and is more correctly termed " Onyx marble or calcite onyx" whereas true onyx is a chalcedony variety. The ornamental stone used by the Mexicans in their crafts is usually acid processed to give the smooth polished looking glaze to this softer, material which is, as you've stated, the result of water deposition of calcite or aragonite. Travertine is often very dense and solid and can be as hard as Mohs 4 depending on silica content etc....mel
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Post by gemkoi on Oct 22, 2006 13:59:14 GMT -5
Chalcedonic Onyx is what you mean Mel, as far as 'ture" onyx. Onyx is a very loose terms which means "layered" I think we both right, but i wouldnt call that stuff travertine. Onyx marble or calcite onyx, sure. But not travertine. I think if either of us were geologist, we could still agrue it. Theres a Marble from near by, which has a travertine like origin. And some folks call it travertine. But it micro crystaline. And pretty hard stuff. BUt its metamorphed and it no longer just Travertine. but Travernic Marble.
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Post by ladyt on Oct 22, 2006 19:31:56 GMT -5
Not to start an argument or anything but... I sent this to norocks. I know it is travertine. It is soft, but you can tumble it. If it goes to long ( more than 5 days) it will disapear. It gets very shiney in polish. I don't know what all the scientific names are, but Travertine it is. I would have to agree with Mels definition. Tonja
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Post by gemkoi on Oct 23, 2006 15:13:53 GMT -5
Your missing the point LadyT,
Travertine is not a mineral or a rock, it is an unclassifiable "mixture" Calcite and aragonite as Mel states would be a common makeup of Travertine, but neither would show a pure form in the mixture And could not be chemically identified in such. Calcium Carbonate is what travertine is classified by from my understanding. This piece in the photo is not Calcium Carbonate. Plus, because travertine can sometimes come in layered formations, the term Onyx can still apply.
And in general terms on the open market, most material being label as "Mexican Onyx" is a travertine, however I stated it was "Onyx from Mexico", not Mexican Onyx. Ive seen thousands of pounds of this Mexican onyx and travertine in the wild. This piece is not those. That’s my point. Sure, it may be made up of minerals that makeup travertine, but doesn’t make it travertine. If you know for certain, I would like to be educated as to why and how this is travertine? Only becasue im here to help educate when questions like these go off point. But if im wrong, i like to know why.
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desertdweller
fully equipped rock polisher
Member since August 2006
Posts: 1,803
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Post by desertdweller on Oct 23, 2006 16:46:19 GMT -5
Hi All, Okay this is my two cents. Shain, from my understanding,Travertine is classified as a variety of limestone. In order to be called a limestone, the rock has to consist of 50% or more of calcite or aragonite. The remainder is made up of impurities that could be rock particles of many kinds. Travertine, technically speaking is a color banded crystalline deposit. Since travertine can be made up of more than 50% calcite, that makes it possible for it to be both non-porous and fairly translucent. It is the calcite that falls under the term "carbonate", not travertine, even though that is what it consists of. I hope that made a little sense, even a tiny wittle bit.
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Post by gemkoi on Oct 23, 2006 18:15:30 GMT -5
from Simon & Schusters Giude to Rocks and Minerals-1998
this is word for word from the book. It says nothing about a crystaline structure as what is in the slab in question. the word "stratifications " means= To form, arrange, or deposit in layers. And this book travertine 'no stratifications but small thin bands differentiated by concentrations of impurities or by grain size."
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Post by ladyt on Oct 23, 2006 20:31:44 GMT -5
Well, what ever it is, when I originally posted the entire rock and asked what it was, freeform responded with definatley travertine. Several other members agreed. I tried to search for the post, but couldn't find it. So I was going on what you told me before. I don't care what it is, I like it and it takes a great polish. It's soft but yet hard. It doesn't break easily in your hand, but if you drop it , it will break. That's all I know.
Tonja
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ZackAttack
starting to shine!
Member since January 2007
Posts: 45
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Post by ZackAttack on Oct 23, 2006 20:37:10 GMT -5
Didn't mean to start something here! Whatever it is, it's rolling in the tumbler as I type.
Hey Shain, would you like me to send you a slab of it, so you can examine it?
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desertdweller
fully equipped rock polisher
Member since August 2006
Posts: 1,803
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Post by desertdweller on Oct 23, 2006 22:44:32 GMT -5
Shain, my information came from Charles W. Chesterman, Honorary Curator of Mineralogy, California Academy of Sciences, he is also the Senior Scientist of California's Division of Mines and Geology, His consultant is Kurt E Lowe, Professor Emeritus of Geology, City University of New York.
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Post by gemkoi on Oct 23, 2006 22:48:51 GMT -5
LadyT, now Im taken personal offense to this. I found the thread after 30minutes of searching. Mel told you that, I never had any input in that thread and if I saw it when it was originally posted, I will be in the same boat. And state the same thing as it not be travertine. forum.rocktumblinghobby.com/index.cgi?board=Pictures&action=display&thread=1155237371Im sorry, but that’s just uncool. Besides, why didn’t you state that originally when I posted my first responds? As now it comes off as plain disrespect and that erks me good. Especially for how much input and help ive given on this board. Because it would make since for you to point that out before, and not after I asked or confronted you on how you knew. I would like to know how many times ive discredited members of this board? I did find a thread were I did try and help ID some stuff for you LadyT, but it wasn’t onyx, at least I don’t mention it in my reply. forum.rocktumblinghobby.com/index.cgi?board=Pictures&action=display&thread=1151608830Troy, I appreciate that offer ;D, but I could send you a bucket of slabs of that stuff. You didn’t start anything. I started it when I disagreed with the majority, though I still disagree and would like to point out for anyone to find a piece of travertine for sale and compare it to that photo. They will all find out the term is loose and what they were sold was Onyx. IF they were sold travertine, it wouldnt look like that stuff. As my agrument is not there isnt Calcite and/or argonite in this stone. But that also doenst make it travertine if there is. A Mineral ID, is not the same as Term ID. Seems like everyone is missing my point.
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Post by ladyt on Oct 24, 2006 5:21:26 GMT -5
Shain, I appologize to you. I have been searching for that thread since this came up and the search didn't find it. I was relying on my memory and as you have pointed out, I was wrong. I would have swore you were the one that helped me id that because you have helped me so much before. it was not meant as disrespet. I will refrain from adding input anymore.
Tonja
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ZackAttack
starting to shine!
Member since January 2007
Posts: 45
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Post by ZackAttack on Oct 24, 2006 6:22:08 GMT -5
OK, so it's a rock ;D let's just drop this thread before friendships are scarred!
Tonja, I forgot that I got this from you till you said so, if I had remembered I would have pmed you and saved all this.
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Post by gemkoi on Oct 24, 2006 13:38:54 GMT -5
LadyT, i accept your apology and didnt mean to be so rude. Just as of late, there seems like either i cant get my point across on this baord, or people are not reading what i am saying. Becasue if anyone was to go into a rock shop and ask to buy "travertine" they would be sent to a tile or landscape shop. And when they see the travertine in question, it wouldnt look anything like the piece in question on this board. Ask for "Onyx" in a rockshop and 90% of the time they will show you this stuff.
Ya, i and tried using the proboards serach feature too, and with no luck. Went into the photos section and spent a while trying to find that thread. So no harm done. ;D
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