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Post by NM Stone Supply on Feb 24, 2007 23:42:47 GMT -5
Can anyone tell me what Opalized wood will look like? I have this piece and It is like glass. Is this just Agatized Wood or could it be Opalized wood?
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Post by stoner on Feb 24, 2007 23:50:54 GMT -5
If it breaks like obsidian and has a shine to it like obsidian when it breaks, it's probably opalized wood.
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Post by NM Stone Supply on Feb 24, 2007 23:54:34 GMT -5
From the outside it just looked like another piece of petrified wood but I started to break it and it looked great inside. It did break like if it was obsidian. I may have found a good piece then.. Thanks
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blarneystone
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Post by blarneystone on Feb 25, 2007 10:50:06 GMT -5
Some of the pet wood I collect is opalized but it took a little research for me to be relatively certain. One of the characteristics I look for is what type of cleavage it has. The way I understand it is that Opal doesn't have a true micro-crystalline structure, it consists of micro-spheres so the cleavage is unpredictable. Fractures can shear in any direction! and chipping it can produce nice concave cleavage.. You can see the concaves in this pic.. This piece was chipped when I found it in the Brazos Rr. so the fracture isn't as crisp as you would think.. it's been worn smooth by river action... You can see in the pic that it's semi-transparent as well, like your's. In your 2nd pic.. that fracture line in the middle is all over the place. i bet it's opal. I have limited experience though so if I'm way off base hopefully someone will jump in here. I'm still not 100% certain I can ID it properly so there you go... I have some of this stuff tumbling right now and it's taking forever in 60/90. ...But it's coming along nicely. It just glows in the sunlight.. beautiful semi-transparent caramel color.. really nice. Hope that helps... Dan
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Sabre52
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Post by Sabre52 on Feb 25, 2007 11:10:44 GMT -5
Not a real wood expert but the opalized wood I've found feels to me to be lighter in weight than the agatized wood and like Dan says, kind of more brittle and prone to fractures in almost any direction......mel
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Post by lbowman1 on Feb 25, 2007 22:15:42 GMT -5
Thats something I've wondered about too. Thanks for the post.
Lori
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Post by gaetzchamp on Feb 26, 2007 1:24:50 GMT -5
So what you're saying is that you can only identify opalized wood by the cleavage and not color?
Gaetz
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Post by puppie96 on Feb 26, 2007 2:10:16 GMT -5
I've been wondering about this too...please keep the help coming...thanks!
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rollingstone
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Post by rollingstone on Feb 26, 2007 2:45:23 GMT -5
Can't say I've tried this, but.... agate has a mohs hardness of 7, while opal has a mohs hardness of 5.5-6.5. So if what you have is opalized wood, if you try to scratch agate with it, it should not leave a scratch (after rubbing off any powder left by the opal). But if you have agatized wood, it should be able to leave a scratch on another agate (same hardness). I think the rough rule of thumb is that you can scratch a rock up to 0.5 mohs units harder than what you are scratching with, so only the hardest opal should be able to leave a scratch on a true agate, and then just barely. -Don
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blarneystone
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Post by blarneystone on Feb 26, 2007 8:58:22 GMT -5
Gaetz - The stuff I find varies in color so I don't think it would be a good way to identify.. I've even seen some that has dendrites on-line: www.fossilmuseum.net/plantfossils/Plantae-sp-indet/plant-fossil-7.htmwww.fossilmall.com/EDCOPE_Enterprises/plants/plfossil7/plant-fossil-7.htmThe piece in those links is exceptional.. Most he stuff I find doesn't have fire but I've found some with a nice sheen.. Here's an excerpt from a good site (link below): Within 10 to 40 million years, the opal of the silicified wood further dehydrates and crystallizes into micro-crystalline quartz (chert). Factors such as temperature and pressure may speed or slow the process, but eventually the opal of the solidified wood becomes chert (Stein 1982). During the change from opal to chert in silicified wood, the relict woody texture may either be retained or lost.
During the silicification process, various materials and minerals may be incorporated into the silica gel. For example, manganese dioxides, iron oxides, organic matter and authegenic clay can alone or in combination color the opal or chert that forms silicified wood. Because each piece of wood becomes silicified in its own local geochemical environment, the trace and major materials and elements that it contains will vary greatly from piece to piece even within the same stratum (Knauth 1972:45; 1981). Therefore, trace element analysis is generally useless in tracing the source of any silicified wood.www.intersurf.com/~chalcedony/Petwood.htmlSo... color will vary depending upon what other minerals and organics may be present. ...and like Don says.. the hardness may vary as well... Pet wood when replaced with Silica will go thorugh various stages as the water content dehydrates.. Opalized wood eventually becomes micro-chrystallin quartz (chert) according to the web page linked above. so cleavage is a good way to tell I think...
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stefan
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Post by stefan on Feb 27, 2007 13:13:45 GMT -5
One of the ways I tell Opalized wood is to look at a clean break- Opalized wood will look "wet" and if sprayed with water (and the opal is not too dried out) it almost beads up on it- Not a real scientific approach- but the 20 to 30 chunks of Opalized wood I have all share this same feature Based on your photo NMOnyx- I would lean more towords and Agatized wood- In the second peicture there is some scaling where you hit it- A classic Agate fracture- But you still Have a WONDERFUL chunk of wood there!!!
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Post by NM Stone Supply on Feb 27, 2007 23:37:09 GMT -5
Thanks for the info.
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WyckedWyre
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Post by WyckedWyre on Feb 28, 2007 8:00:03 GMT -5
Looks agatized to me...Sabre's right. The opalized stuff isn't as heavy and is very, very shiny...almost looks varnished. ::)s
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franzibear
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Post by franzibear on Feb 24, 2009 22:17:49 GMT -5
I get confused about stuff like this, too. I've found some very milky, milky wood, and darned if I know if it's agate or opal. I'm definitely going to keep this thread in my mind.
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MikeS
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Post by MikeS on Feb 24, 2009 22:50:26 GMT -5
one good way to tell is with specific gravity...agate tends to be in the 2.5-2.7 range, opal is usually 2.0-2.3
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1rockhound
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Post by 1rockhound on Feb 26, 2009 11:26:11 GMT -5
To me it looks like a agatized limb cast. Opal tends to have a waxy look to it and very smooth. Another question would be do you know how long it's been out of the ground? If it has been awhile it probably is agate as opal tends to crack or what is called craze and cloud up do to it drying out since opal tends to have a very high water content.
You could also tell just by trying to polish it as opal will grind down much faster than agate.
Jason
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MikeS
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Post by MikeS on Feb 26, 2009 14:38:08 GMT -5
sometimes you get both in a single piece...the Wiggins Fork stuff has both agate and opal in it... The clear part of this limb cast is agate, the white streaks are opal... these are mostly opal, with some agate in them too... Mostly agate, with some opal...
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amznwmn
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Post by amznwmn on Jan 22, 2012 17:02:36 GMT -5
MikeS - I have literally boxes of pieces like the middle picture you posted, except my pieces average about 3-4" long and maybe 2-3" wide, but some are double that.
Yours was the first explanation I've come across as to what exactly I had. I've been calling opalized wood, but I can see from your pictures the difference in the two - opalized vs. agatized (which I have wayyyyyyy too many boxes of).
I appreciate your post clearing up my confusion!
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Post by christopherl1234 on Jan 22, 2012 23:17:14 GMT -5
looks like agagtized wood to me
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Post by johnjsgems on Jan 22, 2012 23:53:46 GMT -5
Agatized. In the mixture pictures you can spot the opalized portions by the definite wet look.
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