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Post by jakesrocks on Jul 15, 2013 13:33:43 GMT -5
Chemically, there is very little difference. Only trace amounts of other minerals which give agate its colors. But Quartz as such is crystaline. Agate is not, except for vugs which may have crystaline quartz in them.
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sheltie
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Post by sheltie on Jul 15, 2013 15:06:51 GMT -5
I appreciate your response but it is still too technical for me (that should give you a clue as to how much I know!). Is there a relatively simple way to distinguish between the two and can you tell what the two pictures are above? I've heard the translucent vs opaque explanation before but there appear to be some pieces that may fit either category.
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Post by jakesrocks on Jul 15, 2013 15:16:01 GMT -5
The pictures you posted, to keep things simple are agate.
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Deleted
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Post by Deleted on Jul 15, 2013 15:16:22 GMT -5
agate equals almost like glass, it may be opaque or water clear quartz equals crystalline, you can see crystals they may be opaque or water clear.
Your piece looks like quartzite. That is a quartz sandstone. Metamorphic in nature with quartz sand having been squished together into a stony mass. Would need better image to see if it's quartzite.
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Post by deb193redux on Jul 15, 2013 16:39:35 GMT -5
To clarify: both agate and quartz are crystalline. Glass and opal are not crystalline. Agate is micro- or crypto-crystalline, while quartz is macro crystalline. If you can see crystal structure it is quartz, or some other mineral. If it is MOHS 7, translucent/transparent, and you can't see crystals (like you can in granite or druse) then it is most likely agate.
Sometimes you might get a piece of a massive crystal, such that you cannot see any internal crystal structure. Then you are in a tight spot, unless you see a fracture plane or distinct outline that corresponds to a crystal habit of quartz.
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Post by Deleted on Jul 15, 2013 17:07:30 GMT -5
Daniel; I was being visual. sheltie is asking for help and making it clear technical answers are beyond his ken. I oversimplified for his benefit. I still think it looks like quartzite.
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Post by deb193redux on Jul 15, 2013 20:29:30 GMT -5
that's ok. visual is good. but, so are precise terms, i do not think think simple accessible explanations are beyond the ken of any adult, but even if it is not to sheltie's taste, he is not the only consumer of this thread. there have been 60 views, and likely many more over time. accuracy is important.
regarding quartzite, that seems possible. if we had a well focused macro shot we should be able to rule that in or out, because quartzite grains are larger than fine sand.
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<'))))>< Fish
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Post by <'))))>< Fish on Jul 15, 2013 21:01:53 GMT -5
All rocks are a type of quartz, except gems ....
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Post by Deleted on Jul 15, 2013 21:40:35 GMT -5
All rocks are a type of quartz, except gems .... Lets not confuse things. Limestone aint quartz or even chemically similar. Jade either.
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<'))))>< Fish
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Post by <'))))>< Fish on Jul 15, 2013 21:48:52 GMT -5
Ok Scott...you right, not all rocks but most all rocks are quarts
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sheltie
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Post by sheltie on Jul 16, 2013 8:33:20 GMT -5
that's ok. visual is good. but, so are precise terms, i do not think think simple accessible explanations are beyond the ken of any adult, but even if it is not to sheltie's taste, he is not the only consumer of this thread. there have been 60 views, and likely many more over time. accuracy is important. regarding quartzite, that seems possible. if we had a well focused macro shot we should be able to rule that in or out, because quartzite grains are larger than fine sand. First to Shotgunner - Thanks for the explanation, it was exactly what I wanted. Clear, concise, to the point and no technical jargon. I never took anything of a scientific nature regarding rocks in either HS or college and the only thing in science that I care about is the beauty of the subject matter at hand. Deb - I really don't care if 1,000 people have viewed this thread. It is MY thread and it deserved the answer Shotgunner gave. If you or anyone feels that the answer should be expanded, start another thread. I agree with you that accuracy is important but I'd also bet that since the question was really so basic that most of the other viewers were much like me and needed help on a basic level. While many on this forum are at an advanced level regarding rocks, gems and minerals when compared to someone like me, there are enough of us who are still at or near the beginner level who appreciate learning in baby steps. When it comes to areas of expertise, all of us have at least one. I happen to have several, none of which are in this particular field. When ANYONE requests information from me in my area of expertise and they ask for the answer at a certain level, i.e., beginner, advanced, whatever, I cater my response to that level. Your comment about simple accessible explanations is insulting and if you reread it I think you would agree.
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Deleted
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Post by Deleted on Jul 16, 2013 11:29:12 GMT -5
I use the break method. If you break a piece of agate it looks like a glass break. If you break a piece of quartz it will be a rough break but if it is broken on one plane the break will be rough but super shinny. When you break quartz in the rough it is really tough and most of the time will crumble a little on the surface where the hammer hit. The piece of agate that breaks off will be really sharp and possibly bury itself in your leg. That is why native Americans used it for arrowheads where there was no chert available.
Once you see the difference with a side by side break it will be real easy to tell. If you are still having a problem telling the difference I will send two examples so you can make positive ID. PM me if you want the samples. And it is no problem because I give away free rock all the time. I have way too much. Jim
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Geoff
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Post by Geoff on Jul 16, 2013 12:37:36 GMT -5
The Quartz Page should help you out immensely. Start on the intro page, which I linked, and explore from there.
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sheltie
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Post by sheltie on Jul 16, 2013 12:49:58 GMT -5
Excellent! Thanks for the link (which also included some terms and words Deb used earlier which I didn't understand and now I do).
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Post by Deleted on Jul 16, 2013 14:13:16 GMT -5
sheltie - Jim @wampidy seems to have a good method. Do you have a piece you can break and see how it breaks?
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