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Post by colorshapetexture on Apr 19, 2011 7:10:51 GMT -5
I had a great time at DH last week. And while talking to Gina she mentioned something new had been found there. She said they had found a couple of real geodes at the machine dig. Now the first thing that came to my mind is the geodes like from Keokuk Iowa, or the Kentucky geodes. Lumpy, bumpy, smoothish, round, hollow, rock balls. Thought those ought to stick out like a sore thumb at DH. As there is nothing I had seen that was round or even close to a geode. Just plates and sharp crystals. Then Gina was looking at my finds and she thinks I had found one of the geodes. In fact she was sure it was one. She told me to cut it open and it would be hollow. I got it home and ran the hose on it and on the back away from the crystals I saw that made me keep the piece, instead of throwing it down the hill was a greasy red mud spot. I hit it with the spray and it started to cav. then a few chunks of mud flew out. Then all the sudden the water spray/splash back just went away and the steam of water went into the vug. And kept going into the vug. Heck I must have shot better than 1/2 gallon in there before it started to fill up. Needless to say I was thinking this is way cool. Held it up to try to get some light in it. Well it was deep and when the light would get in a little I could see nothing but crystals. But still can't see the bottom of it. So today I will pop (cut) this thing open I can't stand it. It is a cool specimen as is so kinda hard to think about cutting on it. But hey Gina said to cut it open. So I will this afternoon. Stay tuned. Here it is. It is really butt ugly except the little crystal cluster. This is the bottom where the vug started. And it goes way in there. Gosh its gonna be hard to cut on this. Then again can't wait to get it open. Cant just cut a little off and look either. I'll have to just pick a spot and cut her down the middle. Would you cut it? lol Later Jim
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Post by rockshine on Apr 19, 2011 7:19:36 GMT -5
Jim, I think today is too soon to cut it open. Think about it a day or so, wash a little more, get a mechanics mirror on a stick and try to look inside, then maybe cut away. Oh, go ahead and cut it. I want to see what's inside, too. Dave
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Post by stairman on Apr 19, 2011 8:30:58 GMT -5
I second the mechanics mirror before you cut it....would be sad to cutright through the best part inside.I gotta come visit that place someday.
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Post by arappaho on Apr 19, 2011 8:44:03 GMT -5
Good luck, Jim! I can't look. Gotta wonder if cracking it open with the old chain and wench method might be better? Joe
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Post by colorshapetexture on Apr 19, 2011 9:03:06 GMT -5
I don't know Joe. The walls are not like a normal geode. Not a round cavity with points toward the center. Seems a bohoydral wall with druze? Yea it would be solid pressure points all the way around but it looks like it would break real crazy. Or just crush one of the little pocket thingies in the side. I promise I will look a bunch more. Thanks for the warnings all. Now I'm becoming nervous about doing it. lol Heck I was just gonna go out and wack it open on the ole saw. Now? MAGMA Rocks. What a learning experience.
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Post by lauriesrocks on Apr 19, 2011 10:16:26 GMT -5
I don't believe you can call that a geode. Geodes are formed in a particular way. Just because it is a round cavity or has a rounded outer shape, does not make it a geode. The veins at Diamond Hill were formed by hydrothermal solutions, geodes have crystals generally deposited by meteoric water. The term vug would be more appropriate. It is the mode of formation that determines a geode, not the shape. Geodes are found in sedimentary rocks, usually limestone, or in volcanic rocks, where voids are created by gas. Despite what it says on Wikipedia and similar non-scientific sites, hydrothermal solutions are not responsible for the slow process of crystal formation in geodes.
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Post by Barrett on Apr 19, 2011 11:26:31 GMT -5
Great info, Laurie. I did not know that but always wondered.
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Post by arappaho on Apr 19, 2011 12:46:45 GMT -5
You're probably right, Jim, the crackin' method may end you up with a bazillion pieces. I am just trying to think of a way to let it split on it's own, so any big crystals "might" just "separate" in one piece. Of course I haven't seen it, but I might be tempted to try and get a crack going with a well placed sharp chisel or two. Or you could just cut it. Joe
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Post by auplater on Apr 19, 2011 13:58:46 GMT -5
I agree, vug is probably correct. It'll probably look like these inside from our massive boulder from February 2011: here's how I split mine... John L
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Post by chet on Apr 19, 2011 15:28:39 GMT -5
There is a specimen shown at this website: www.gamineral.org/DHMiscellaneousPage.htmlWe call it a "two chambered geode". Do you think it best to call this a geode or a vug? You can see the specimen is cleanly broken into two halves, and there does not appear to be a channel connecting the inside to the outside.
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Post by gsellis on Apr 19, 2011 15:39:36 GMT -5
An autonomous vug? A permiscuous vug?
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Post by lauriesrocks on Apr 19, 2011 16:04:37 GMT -5
Chet, in my opinion, you would not call it a geode, for precisely the reasons I stated above. I know there is an irresistible urge to call something that looks like a geode, a geode, but I do not believe you can have a true geode in a classic hydrothermal vein deposit like Diamond Hill. Out of the tens of thousands of specimens that have been collected there, it stands to reason that a few will feature rounded cavities, rounded exteriors, or even both, but this does not mean they are geodes. Something else is important to note about geodes. At the places where they are formed, they occur in large numbers, usually in the tens of thousands.
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Post by JohnD on Apr 19, 2011 17:28:04 GMT -5
I definitely would not call it a geode. Vug is right.
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Post by mickey on Apr 19, 2011 17:58:27 GMT -5
I guess it depends on how you define geode. Several definitions that I have seen do not consider formation conditions but rather how the rock looks. Geologically speaking, geodes are found in sedimentary and volcanic rocks as opposed to hydrothemal veins and rocks. However, I have not seen anything that says that a hollow rock filled with crystals formed by hydrothemal conditions is not a geode. If it has an obvious opening, then I would not call it a geode either. On the other hand, don't geodes from in vugs?
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Post by lauriesrocks on Apr 19, 2011 18:22:17 GMT -5
It is easy to find definitions on the internet that will support anything you want to believe. You are welcome to call them geodes or anything you want. Call quartz calcite. I'm sure some will agree with you.
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Post by lauriesrocks on Apr 19, 2011 19:03:45 GMT -5
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Post by mickey on Apr 19, 2011 22:57:48 GMT -5
Laurie, Guri is a sophomore at the University of Florida and is very knowledgeable about rocks, but I wish he had posted more about Steven Garza's credentials and his sources. According to Brad Cross and June Culp Zeitner in "Geodes: Nature's Treasures" a geode is defined as "A natural inorganic object, most often chalcedony, which are or have been hollow. Geodes are roughly spherical and can occur in igneous or sedimentary rock. The interior may be lined with crystals, including quartz as well as other minerals, pointing toward the center. " This definition does not rule out other types of geode formation. Garza only rules out metamorphic rock because the intense pressure would not allow cavities. He makes no mention of hydrothermal conditions and only considers dissolved silica to form geodes. In Florida, we have many "rocks" composed of calcite that are completely enclosed with calcite crystals on the inside that have weathered out or formed in limestone. I still call them geodes. While I'm not sure what conditions polyhedroids formed, they are considered geodes and are not spherical and are formed after the replacement of calcite. While it may be wrong, any spherical, hollow rock that I pick up that is completely enclosed and has crystals on the inside, I will call a geode and not a vug. Sincerely, Mickey
(corrected spelling of polyhedroids)
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Post by Barrett on Apr 20, 2011 1:09:24 GMT -5
Tricky subject. I tend to think a geode was formed from gas bubbles ... not from elements that crystillized during cooling but from elements that percolated or seeped in over time. Take for instance, all the millions of the most famous geodes their are, the Brazilian amethyst geodes. You see a geode aka. amygdaloids that form in basalt, like the brazilian amethyst geodes, when they cool the trapped gases seep out and leave a vacumn chamber with no amethyst crystals. It's the tiny microscopic fractures that developed in the basalt that allow rainwater and other fluids to circulate in the still cooling mass, which then deposit the silica and other minerals to form crystals. I would call that a secondary water/silica deposit.... where as Diamond Hill amethyst take water directly from the ground in a primary event depositing the silica to form crystals. It was always my understanding that geodes formed from secondary events and places like JXR and Diamond hill formed from primary events. Some Jackson crossroads amethyst formed in completely sealed off cavities and/or gas bubbles but the crystals crystallized when those gas bubbles cooled down and used what was in them(the vesicles) to form, where as geodes were for the most part empty and then took in minerals and fluids at a later stage and through different geothermal processes. Of course it can swing both ways with this argument and i am sure many examples can be brought to light on both sides to back it up.
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Post by lauriesrocks on Apr 20, 2011 5:57:14 GMT -5
Amguy, the Jacksons Crossroads deposit is identical in origin to Diamond Hill, by hydrothermal solutions. There were no gas bubbles, they occur in the amygdaloidal basalts. If we take the argument that shape determines if it is a geode or not, then think of the classic Brazillian amethyst geodes. I think EVERYONE would agree that these are geodes. But look at the large variation in their shapes. None are round, most are oval, some are very elongated ovals, and some are completely irregular in shape. So if we extend this analogy, we would then have to conclude that any oval cavity is also a geode, or that any irregular cavity is also a geode. But this would be just silly. If you do a google search and type in "definition of geode", it is absolutely amazing the ridiculous definitions that come up. The first one is from merriam-Webster: "A small cavity in rock lined with crystals or other mineral matter". If this were true, then ANY vug or cavity would be a geode! Clay is mineral matter, so if you have a piece of granite with a depression in it with clay stuck inside, it would be a geode! NONSENSE. The entire first page of this google search is full of similarly pathetic and unscientific definitions. Again, I really couldn't care less what anyone chooses to call their own specimens, but that does not mean that what they call them is scientifically accurate. As for June Culp Zeitner. A wonderful woman who contributed greatly to our hobby. Her articles and books have been a great boon to many, many rockhounds. However, she is notorious for innacuracies! There are literally hundreds of examples in Appalachian Mineral and Gem Trails. She would take an original quote from a geologic report or historical treatise, and reword it in such a way as to completely alter its meaning in a misleading way. Again, I think she was a great woman, but I would not use her to bolster an argument about accurate definitions.
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Post by mickey on Apr 20, 2011 9:05:03 GMT -5
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Post by lauriesrocks on Apr 20, 2011 9:19:32 GMT -5
By citing that definition, you just made my point! I guess you didn't see the post I made just before yours.
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Post by mickey on Apr 20, 2011 9:23:27 GMT -5
Of course, I did.
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Post by lauriesrocks on Apr 20, 2011 10:02:55 GMT -5
Merriam webster can't even agree on their own definition. First the say "A small cavity in rock lined with crystals or other mineral matter." Then on the same page of a google search, say "A nodule of stone having a cavity lined with crystals or mineral matter." You would think they could at least be consistent in their bogus definitions. Just because it's on the net or in print, doesn't make it so.
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Post by mickey on Apr 20, 2011 10:26:49 GMT -5
"Just because it's on the net or in print, doesn't make it so." To this, we both agree.
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Post by Barrett on Apr 20, 2011 10:55:54 GMT -5
I was agreeing with you Laurie. The crystals formed from hydrothermal action from a primary event where as geodes, in my opinion, formed well after the gas bubbles were formed from a seperate water/silica deposit..generally water slowly percolating into the cavitiy to line it with crystals.(aka brazil ammy geodes, most agates, etc.
Actually, JXR did have gas bubbles..MinRec: vol. 36 number 6...(Abbreviated).
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Post by rockshine on Apr 20, 2011 12:25:17 GMT -5
a rose by any other name...might be an apple, but hardly ever an onion. But whatever they are called, I like 'em.
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Post by colorshapetexture on Apr 20, 2011 12:51:13 GMT -5
I vote for..................... Diamond Hill Cathedrals.
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Post by scott on Apr 20, 2011 15:35:54 GMT -5
Pluto suffered a similar type controversy as its planetary rank was yanked and replaced with "dwarf planet" changing our 9 planet solar system to 8. Many people including children will probably refuse to acknowledge this change for the rest of their lives. I think there is scientific merit to classify things based on exact definitions else things begin to overlap and things can become difficult to classify. Heck, look at the whole jasper, chacedony, agate, etc. controversy. It is nice to know exactly what someone is referring to by the use of one word. For example schorl is the black variety of tourmaline. I would rather a person tell me schorl than tourmaline when describing a specimen because I would get an immediate and more accurate picture in my head. But Groups, Classes, and subclasses, etc., are all necessary and useful for classification. If a geode could fall into a class, or group type category then perhaps a little generality can be permitted in which case vug type cavities might be considered a geode. I'm sure that whoever first defined the word geode couldn't have imagined the vast variety of crystal lined cavities there are in the world. So now we are left with another term from which can be interpreted in many ways from a simple printed definition. I think I prefer Lauries definition of a geode simply because it's what I've always seen and handled when dealing with them. However, I might have a different perspective if my experiences were different.
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Post by Ryan on Apr 21, 2011 23:47:49 GMT -5
Yes Scott, I want Pluto to be a planet also. But only because I was TAUGHT it was a planet. Now that I have learned more information, primarily of the existance of Quoarar and Sedna, along with sundry other Kuiper Belt objects, I see the wisdom in excommunicating Pluto. If we had not, the solar system would now have 11 or 12 planets and counting as we continue to discover planetoids and other escaped moons of the gas giants that have assumed elliptical orbits deep in the outer regions of the solar system.
My point is this, No one here sat on the comittee that determined what exactly constitutes a geode. Though that said; I agree most with Laurie and yourself, Scott, because the more thoroughly and specifically we classify things, the more information is conveyed by its name alone. I especially like your schorl vs. tourmaline example. If you say "tourmaline", for whatever reason, I picture a watermelon tourm. All schorl is tourm, but not all tourm is schorl.
Thus, Geodes are rounded rock hollows with crystals inside, but not all hollow crystal bearing rocks are Geodes. The very essence of high quality communication is the sharing of accurate and efficient information. If we allow ourselves to be leinient or sloppy with our classifications, then accuracy of the information goes out the window. Suddenly all beryl is "aquamarine" and all corundum is a "ruby" when we know in reality that those statements are not valid. Flip them around and they become valid.
Is this an anal retentive view on things? Possibly... Probably... But our scientific forefathers didnt travel to the galopagos, invent the telescope, stand trials in front of an angry church officials and irradiate/shock/poison/sicken themselves to discover FACT just so future generations of scientists could be willie-nillie with the information they discovered and render their sacrifices in vain.
Thats my two bits. Sorry, I had to jump in...
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Post by Ryan on Apr 22, 2011 22:13:22 GMT -5
Durn it Rick, I was feelin all smart and stuff and you had to sink my boat! lol
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