Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: jemmatcf on 19/04/2010 03:16:24
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I found this rock laying in a bush in my front yard. I live in northwest Georgia.
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These look more like crystal "ghosts" to me. The rock appears to be all quartz but that could just be the photograph. Can you scratch the rock with a knife? Does the rock look milky?
With all I can see - the blackish veins in the rock and what looks to be quartz crystalline structure makes me think these are places where crystals one occurred by for some reason have been dissolve or fallen out.
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The whole rock is milky white and shiney. The dark spots look almost metallic or slightly rusty. When I scrapped with a knife nothing really happened.
Thanks so much for your reply!
Joe
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here's another view.
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Looking at this on my cell phone, so not really clear- but my guess would be either garnets or pyritohedrons. But as well as I can see the photo, those could be Geezer's age spots?
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Oi! I resemble that remark!
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Thanks! I'm no geologist but they do look like the garnets in this image:
http://www.cs.cmu.edu/~adg/images/minerals/pygarnets/garnetrock.jpg
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Ah-er-um
I forgot about garnets. But the matrix - that still looks like quartz to me. Bass is off doing his Monty Python imitation of "I'm a lumberjack and I'm OK" so can't really see it.
He is too cheap for a laptop.
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Thanks so much for all your replies. After looking at lots of pictures of Milky White Quartz on the internet, I am sure that's what the 'matrix' or the big white rock with the dark spots on it is. There are tons of this rock all over my front and back yard. From cantalope size chunks to tiny thin flakes. Being such a bright shiney white it really stands outs and is easy to find. Unfortunately for my lawn, once you get past the 1/4 of top soil there is nothing but bright orange clay for at least 3 or 4 feet down (the deepest I've had the pleasure of digging) and most of the quartz I've found is on the surface.
One other interesting thing I have found, which is definitely not milky white quartz is the following which was buried under just under the surface and had small roots growing through it. Any help id'ing it would be great!
Thanks again everybody!
Joe
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From cantalope size chunks to tiny thin flakes.
Are the "tiny thin flakes" actually planar...flakey? or more splintery?
If they are planar, I would suspect that there is something in addition to the quartz. Maybe microcline or sanidine? Though its a bit hard to tell for sure in the photo, it looks like there may be a couple of exposed cleavage planes. As for the black hexagonal spots, it looks like garnets. Did you try scratching the dark crystals with a knife?
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Little Green Grasshopper - That appears to be a sedimentary rock called a "F-O-S-S-I-L" They are the remains of once living things. You have seen something almost identical at my place. In fact, you have commented on it. Do you remembered the name you gave it then???
(Apprentices! Can't get it right to save their life!)
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Also, Grasshopper, did you read the post?
One other interesting thing I have found, which is definitely not milky white quartz is the following which was buried under just under the surface and had small roots growing through it.
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Oh JimBob...you of all people should know that I can at least tell silica from carbonate. I may be a little wet behind the ears, but Im not at the top of my class at a prestigious geoscience college for nuthin.
I was referring to the aforementioned pegmatite. See:
Here is discussion on granite
Thanks so much for all your replies. After looking at lots of pictures of Milky White Quartz on the internet, I am sure that's what the 'matrix' or the big white rock with the dark spots on it is. There are tons of this rock all over my front and back yard. From cantalope size chunks to tiny thin flakes. Being such a bright shiney white it really stands outs and is easy to find. Unfortunately for my lawn, once you get past the 1/4 of top soil there is nothing but bright orange clay for at least 3 or 4 feet down (the deepest I've had the pleasure of digging) and most of the quartz I've found is on the surface.
And here begins discussion on carbonate
One other interesting thing I have found, which is definitely not milky white quartz is the following which was buried under just under the surface and had small roots growing through it. Any help id'ing it would be great!
Thanks again everybody!
Joe
btw, Joe...would you happen to have clearer pictures of the last rock that you posted?
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If JimBob would get those ridiculous half pingpong balls off his eyes he might be able to see what's going on.
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1) The first rock I posted with the dark spots did have a crack in it, and the rock split in two with a couple of bangs on the ground. I scratched the black hex spots with a knife and they fell out in little powdery pieces.
2) Here's another look at the second rock I posted.
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1) The first rock I posted with the dark spots did have a crack in it, and the rock split in two with a couple of bangs on the ground. I scratched the black hex spots with a knife and they fell out in little powdery pieces.
When you split the rock open, were the hex spots elongated like haxagonal columns or were they more roundish? The fact that you were able to scrape them out would indicate that they werent garnets, or that they were heavily altered. Whatever it was, it was heavily altered. Ive had discuassions with JimBob and my petrology professor, and both seem to be in agreement that they likely are not garnets...maybe tourmaline or hornblende.
As for the second rock, it looks to be some sort of carbonate, but beyond that I cant really tell. You can see what appears to be bedding laminations, but I assume that the holes are vugs and from the roots growing through it.
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i can see the southern cross constellation in there..
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If JimBob would get those ridiculous half pingpong balls off his eyes he might be able to see what's going on.
If little green frethac would be clear, as is required of a scientist, he would have not confused the issue. I have castigate him in private. It reflects poorly on my tutelage, even if, as in this case, the student is somewhat more quasi-intelligent than average.
Mind your own business, old man. I like the Grouch Marks mask
As for i can see the southern cross constellation in there..
Baily obviously means this to be reference to an alien relic.
I think the last it is probably some layered limestone with what appear to be karst features. These holes could originally have been filled of softer carbonate mudstone in the matrix - who knows: burrows, a specific types of Pennsylvanian a or Permian tabular coral, or a sport of nature.
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Mind your own business, old man. I like the Grouch Marks mask
That's pretty good coming from an old fossil like yourself.
BTW, Grouchy Marks was the guy that started Marks & Spencer.
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Mind your own business, old man. I like the Grouch Marks mask
That's pretty good coming from an old fossil like yourself.
BTW, Grouchy Marks was the guy that started Marks & Spencer.
Is that where you the S&M gear you keep going on about?
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Ah-er-um
I forgot about garnets. But the matrix - that still looks like quartz to me. Bass is off doing his Monty Python imitation of "I'm a lumberjack and I'm OK" so can't really see it.
He is too cheap for a laptop.
How'd you know I wear high heels??????
must be a peeping Jim [:o]
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Biotite perchance?
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Aye, laddie, 'tis a possibility - much more likely than garnet.
I raised this possibility with frethack when he cam over this Sunday for a visit. It came up in a wide ranging discussion of a lot of things spanning a wide range of topics, from the level of the suns activity to the type off revolver to use for self defense at home. The best would be a 12 gauge revolver - if it could be held in your hand. I think we decided that a sawed off Remington 12 gauge simi-auto shotgun was the best weapon, if one is not afraid of loosing one's hearing by firing it the house.
I vote for mica.