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Post by felton on Oct 25, 2009 23:52:29 GMT -5
I found this guy in the woods by itself in Chapel Hill. I thought it was quartz on it, but it was too fragile. Fingernails won't harm it, but a knife blade will, and I didn't get anything from the blacklight. In case anyone was wondering, the pet wood log is from the Treyburn country club in Durham...I had to show it off to someone...lol.     |
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Post by felton on Oct 25, 2009 23:54:08 GMT -5
Hmmmm....let me know if the pics are too large. I have them set for 1000 X 750
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Post by amythestguy on Oct 26, 2009 2:12:43 GMT -5
It actually looks like one of the members of the plagioclase feldspars with some polysynthetic twinning
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Post by romare on Oct 26, 2009 6:33:41 GMT -5
Definitely looks to be feldspar.
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Post by arappaho on Oct 26, 2009 7:10:24 GMT -5
I'm glad you found this board, felton, because you sure have found
some nice specimens from around here!
The white on that rock looks like calcite and the State may be interested
in that piece of pet wood for the museum too! Nice Finds!
Joe
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Post by earthnhands on Oct 26, 2009 8:47:54 GMT -5
Calcite. And a KILLER piece of wood!
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Post by lauriesrocks on Oct 26, 2009 9:40:39 GMT -5
Calcite, without question. Put a drop of muriatic acid on it and you'll see it fizz.
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Post by amythestguy on Oct 26, 2009 14:26:21 GMT -5
umm..I will have to beg to differ..Feldspars have two cleavage planes that intersect at 90°. Fragments of pure feldspar crystals thus tend to form rectangular blocks. Don't look only at the nice blocky smooth part, look at the rest of the stone. Those surface striations toward the right are seen on some cleavages of plagioclase..sometimes called "veinlets" or [striations]. Make sure to not look at the nice blocky portion..if you take a large chunk of feldspar and break it it will look like that all nice and neat with 90 degree angles..but look at the more natural sections that have not broken towards the right side of the rock..as you can see the 90 degree angles have disappeard..calcite will show those all(clean angles) over due to any breakage and will not metamorph into what looks like melted rock with angles in different direction with no discernable planes which feldspar will..just look at the whole right side of the rock..no angles..no planar faces..justr morphed rock..yes? no? anybody else want to jump in?
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Post by carnelianpete on Oct 26, 2009 15:46:43 GMT -5
Amguy may be right but I think there is a much easier explanation. "Finger nails won't harm it but a blade knife will" If I'm not mistaken I can put a scratch in calcite with my finger nail or at least I have with some of the calcites I have found in the trap rock quarries here in NJ but definitely not feldspar. And as already mentioned put some muriatic acid or even vinegar on it and if it fizzes it is calcite. Case closed.
This just goes to show you that you should use more than one test to identify a mineral species. Always use more than one. It can be the difference between looking knowledgeable and looking like a fool. An example of this would be say you had two pieces of water clear, no crystal structure, no flaws, no opacity chunks of a mineral. Identify the two. If you knew they came from some place that could claim quartz and topaz to be found (Morefield Mine in Va. has the exact material I am describing) it could be either one. What two tests would you use to tell which is which. I personally would use hardness and SG (Density). The SG between topaz and quartz is big enough that you should be able to tell which is which from that alone but I think using just hardness on the two would not be enough to identify them or just SG or just crystal structure it can lead you down the wrong path to identifying a mineral. There are to many minerals out there that can pass for another based on just one test. That would be like trying to pick out the diamond from from several cut stones in front of you based on the fire/brilliancy the stone gives off and that is the only test you use. Would you buy a diamond on that alone? It could be man made or zircon. Both could pass for natural diamonds on looks alone. If you would I have a few stones I would like to sell you. This is just the chemist coming out in me. I never base a test result on one test, better with two and I prefer 3. Sorry for the rambling on.
Pete
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Post by felton on Oct 26, 2009 16:50:51 GMT -5
Wow, a lot of info! I tried apple cider vinegar with no effect, not even on the particles scraped off. I used of all my acid, cleaning off the last paver patio I installed, but I'll grab another jug soon.
As for the pet wood, I know where theres some good 2 to maybe 4 ft logs are, but you'll need a small army to get them out. Since i'm moving to S.C. I'll probabally not be able to get them anytime soon...
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Post by earthnhands on Oct 26, 2009 17:04:17 GMT -5
Felton, those logs need to be pulled out and looked at. As far as I know, 2' and 4' petrified logs are definitely worthy of the effort. You are very lucky to have found them. If you need a small army, you have come to the right place! You wouldn't believe how many of us will come together for such an endeavor. MAGMA has many members in NC. Post a new thread and ask for help. You would be surprized what this group can do, and I bet it would only take a couple of people. I know a few MAGMA members that would definitely love to see them come out of the ground...me included. And please do the test with regular white vinegar so we won't be going crazy with anticipation. Cause I still think it is calcite...with the right side just being weathered calcite.  |
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Post by arappaho on Oct 26, 2009 18:29:00 GMT -5
Dang Felton! You got us goin'now! ;D Pete, Great point that can't be brought up too often. Doing more than one test just plain simplifies things, not to mention getting the right answer.  Amguy, Thank you for your arguement. Let's do it some more! I understand what you are saying about the plagioclase-like striations. Feldspar can be a tough rock to pin down. I've been working on it for years and don't know if I've figured anything out yet. The clear feldspars are the ones that give me a headache. When is it feldspar and when is it quartz? They all have those striation lines, but I guess it makes a big difference what direction they are running as far as looking for a "field sign" goes. But I'll have to stick to calcite for feltons rock, mainly because it comes from my "Home Turf" and I've seen it a plenty. Just so happens I have a piece right here.  I know my pics don't help much, but this is from the same area as feltons rock. I hope you can see the calcite 'structure' on the left and the flat or massive area lower right. That area has criss- crossing striations. They look alot like the striations that you are talking about, if they only went in one direction. But these are more like the "veinlets" you mentioned and are in two directions roughly 90 degrees to each other. I don't know if any of this will be of any help, but here's a 'close-up' of that lower right area that I'm sure will be totally useless.   Now, I drink alot of milk, and I can barely scratch any of this with my fingernail. But I can scratch some of it with my fingernail. I haven't tried the acid test, because I allready know it's calcite because it will fluoresce a pretty pink-red to light purple. Why feltons doesn't, I don't know. felton, I guess you better try the acid test, and the ultra-violet test again. Make sure it's good and dark in the room when you test it. Too bad you're in the process of moving. I've been collecting rhyolite from the Mt. Tirzah area for years. Probably seen your foot prints. And what earthnhands said about retreiving those logs is absolutely true. If you need an army to get a rock out of the ground, YOU'VE COME TO THE RIGHT PLACE! And that ain't just whistlin' dixie........ ;D Joe |
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Post by amythestguy on Oct 26, 2009 18:42:11 GMT -5
Wow looks very similar,
Joe you may want to try the acid test because quote "frequently the feldspars are fluorescent. The fluorescence of the feldspars comes in quite a few different reds from pink to a deep velvety red. I have
some very bright light blue fluorescening feldspars from both Italy and
Pakistan. This blue is close to scheelitte blue. Some times there is a dual
fluorescence with the pink and light blue possibly indicating two different
feldspars with different activators. There is a blue-purple fluorescence
from some feldspars. I have a feldspar that fluoresces light yellow. At
this point I do not know what the activator is. So, yes the feldspars
fluoresce ."
If you think the vinager test works put some on there and see what it does, joe.
Get back to us with the results..but the mystery continues..da..da..duuummm
dolomite?
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Post by pegmatite on Oct 26, 2009 19:05:26 GMT -5
If you try using a weak acid like vinegar or citric acid (lemon juice) be sure and powder the material you want to test first. That will usually give you a much more definitive test than testing a large solid chunk. Don't get too hung up on fluorescence because lots of calcite and lots of feldspar won't react to UV light at all, other than reflecting the UV light. Sure looks like calcite to me.
Steve
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Post by arappaho on Oct 26, 2009 19:45:04 GMT -5
Hey Steve! Good points. 1. Prepare the specimen properly for a good test result. 2. I've got a lot of fluorite that doesn't fluoresce but reflects the light nicely. Allright Jason, That's news to me about different feldspars being fluorescent. Thanks. And as I was walking out to the shed to try a little muratic on a specimen of this stuff, I was pulling for you. I kind-of like having my world rocked, when it comes to rocks, and if this stuff that we've ALWAYS called calcite turns out to be some other animal, then that would qualify! This is a different specimen, from the same area, with a little muratic on it.  But we reely do need to work on the identification of our local feldspars. Where ever that may be. Joe |
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Post by amythestguy on Oct 26, 2009 19:48:38 GMT -5
LOL..I knew you would run out to the ole' shed whether hell or high water..well done my good man
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Post by amythestguy on Oct 26, 2009 19:57:38 GMT -5
What about the penny test? Only problem is it will also scratch dolomite so wouldn't distinguish between those two(calcite and dolomite)..hey felton try scratching it with a penny
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Post by arappaho on Oct 26, 2009 20:11:05 GMT -5
Or just call it CALCITE allready! ;D
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Post by felton on Oct 26, 2009 20:49:33 GMT -5
Ok, both 1970 and 1998 penny was tougher than the mystery material, which shall now be named calcite.....for now..lol.
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Post by amythestguy on Oct 26, 2009 21:22:56 GMT -5
so they[pennies] scratched the material?..if so..then i concede Mr. arrapho[as i am bowing] ;D
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Post by felton on Oct 26, 2009 22:09:28 GMT -5
Yep, both the 95% copper and the 97.5% zinc scratched it...( didn't know if it would make a difference, so I tried 'em both)
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Post by 4cornersrocks on Nov 6, 2009 22:02:07 GMT -5
I find loads of calcite like that here, gotta be calcite.
To carry a big log you just need loads of adrenaline. My wife and I carried a 5 foot long by 1 foot wide log uphill about 1/4 mile one time only to find that when we got home it could not be lifted! I guess we were pretty excited.
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