|
|
Post by johnw on Aug 25, 2018 23:08:11 GMT -5
I need to have somebody kindly explain how this piece came into being. What type of chaos in the limestone deposits in Chihuahua where this was born caused these abnormalities to occur.? Can anyone help share this knowledge? Cheers, johnw 
Photo by Taasha
|
|
fishnpinball
Cave Dweller 
So much to learn, so little time
Member since March 2017
Posts: 1,491 
|
Post by fishnpinball on Aug 25, 2018 23:30:31 GMT -5
One layer at a time.
|
|
Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on Aug 25, 2018 23:55:11 GMT -5
Indeed. Much of the intricacy can be explained by sagenite needles first forming in a void. The agate layers, in varied colors/shades, formed around individual needles, then merged with agate layers forming around adjacent needles. The agate kept growing even after the ends of the needles had been covered, forming the botryoidal top of the formation. Definitely was an active formation, with hydrothermal waters bearing pulses of different minerals in different saturations: made for some fantastic patterns. |
|
|
|
Post by johnw on Aug 26, 2018 13:20:06 GMT -5
Indeed. Much of the intricacy can be explained by sagenite needles first forming in a void. The agate layers, in varied colors/shades, formed around individual needles, then merged with agate layers forming around adjacent needles. The agate kept growing even after the ends of the needles had been covered, forming the botryoidal top of the formation. Definitely was an active formation, with hydrothermal waters bearing pulses of different minerals in different saturations: made for some fantastic patterns. Hello rocks2dust, thank's for the explanation, I can get my head around what you have described, but, I have another observation: yep, from the shape and configuration of this piece it was involved in an exceedingly active formation, however what I cannot fathom is why the egg shaped pieces always project up and are, well just egg shaped, or round as a ball and always smooth? And, as I will show in another piece, have egg colored interiors? Is this just happenstance? When I look at Bahia agates, the interiors are always random and without singular form, the layers flow generally following the curvature of the vessel, whereas the layers of MCLA pieces from Chihuahua are all over the place in really phenomenal mind blowing patterns, or eggs? Cheers, johnw  Here is the egg yoke piece, one white one yellow, just like an egg? Is this just random happenings due to specific minerals flowing around over time? But being the case, why would the mineral just congregate in that one area? Really fascinating for me. But the best part I love about this hobby of ours is we collect these pieces and hold in our hands something that's over 50 million years old. Awesome. BTW, the photo is by Taasha and the piece I purchase from bluemountainjaspermine on eBay. I said I would give them a shout out, which I have done. Is this against any rules? Cheers, johnw  |
|
Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,497
|
Post by Sabre52 on Aug 26, 2018 13:45:26 GMT -5
The crazy lace veins come in a limestone formation matrix that has dogtooth aragonite/calcite crystals. The botryoidal formations in the agate are pseudomorphs ( layered agate replacements) after the aragonite crystals and therefore form those geometric shaped bands you see upper center in your pic. One of the crazy lace types listed in Cross's Agates of Northern Mexico books is actually named " Dogtooth Lace Agate" after the pseudomorphs after dogtooth calcite/aragonite.....Mel
|
|
|
|
Post by johnw on Aug 26, 2018 14:01:18 GMT -5
The crazy lace veins come in a limestone formation matrix that has dogtooth aragonite/calcite crystals. The botryoidal formations in the agate are pseudomorphs ( layered agate replacements) after the aragonite crystals and therefore form those geometric shaped bands you see upper center in your pic. One of the crazy lace types listed in Cross's Agates of Northern Mexico books is actually named " Dogtooth Lace Agate" after the pseudomorphs after dogtooth calcite/aragonite.....Mel Hi Mel, thanks for this. Still cannot grasp the "egg"formations and cause thereof. Do you recommend the book you referenced? Cheers, johnw Follow up on the book......I just checked on Amazon and they are offering it as 1 Used from $632.42. It has to be an awesome book for that price, but....errr, unfortunately, its slightly out of my league.........  . Cheers, johnw |
|
Deleted
Deleted Member
Member since January 1970
Posts: 0
|
Post by Deleted on Aug 26, 2018 16:15:30 GMT -5
Orb-type formations in agate can depend on where in the void they occur. Some short, drip-type hemispheres can occur on the tops and bottoms of enclosed voids (as well as thinly on sides in some vesicular gas pockets). Yes, they can result from pseudomorphs, but botryoidal agate formations do not usually result from replacement of another mineral with a botryoidal habit/texture. In Mexican Crazy Lace and similar lace agates from elsewhere, one can usually find one or more types of sagenite in sliced pieces. Since there seems to be a lot of iron in Mexican Crazy Lace, I suspect that the needles are/were limonite (the red and yellow colors around the cores probably came from that iron). In agate, sagenite does not refer to a specific mineral (mineralogically, "sagenite" only refers a twinning habit of the mineral rutile) and can be any of several minerals with needle-like or fibrous crystals, including limonite, rutile, calcite, amphibole, etc. Whether rutile or some other mineral, they often grow in acicular (radiating from a central growth point) formations. This can form the substrate on which botryoidal formations grow. In some cases, the sagenite puff, pom pom or dome is a prominent feature in sagenitic agate, while in other cases, the sagenite is only a single needle, or so fine, widely spaced or short that one must look carefully at the walls of the void to detect them. In addition, agate itself has a fibrous structure of stacked crypto-crystals (both in quartzine, lutecite/moganite and length-fast chalcedony) that can form short acicular clusters of needles, leading to botryoidal formations on surfaces. Throw some other forms of quartz into the mix (microquartz, moganite and/or macrocrystaline quartz) and you can get some fascinating structures. So botryoidal formations can form in the absence of sagenite. However, agate is almost never pure silicon dioxide quartz of any variety, and what we call agate seems to form most readily where mineral crystals already exist as a substrate. Addition of other minerals can also give rise to strong colors and optical phenomena (such as fire agate). The Mindat article on chalcedony may be a good starting point for gathering more info. |
|
|
|
Post by deb193redux on Aug 26, 2018 17:37:51 GMT -5
radial (hemi-spherical) crystallization of the agate makes the domes. This happens with both primate agate bands, and when as a psuedomorph over an existing crystal of another mineral. Banding is often much smaller scale layer of radial hemi-spheres on top of the layer of domes.
the basic answer is close together radial spheres or hemi-spheres, and then layers of new agate bands across the Botryoidal surface. This occurs in many minerals.
From wikipedia:
"Botryoidal minerals form when many nearby nuclei, specks of sand, dust, or other particles, are present. Acicular or fibrous crystals grow radially around the nuclei at the same rate, appearing as spheres. Eventually, these spheres abut or overlap with those that are nearby. These nearby spheres are then fused together to form the botryoidal cluster."
|
|
|
|
Post by johnw on Aug 26, 2018 21:48:11 GMT -5
Orb-type formations in agate can depend on where in the void they occur. Some short, drip-type hemispheres can occur on the tops and bottoms of enclosed voids (as well as thinly on sides in some vesicular gas pockets). Yes, they can result from pseudomorphs, but botryoidal agate formations do not usually result from replacement of another mineral with a botryoidal habit/texture. In Mexican Crazy Lace and similar lace agates from elsewhere, one can usually find one or more types of sagenite in sliced pieces. Since there seems to be a lot of iron in Mexican Crazy Lace, I suspect that the needles are/were limonite (the red and yellow colors around the cores probably came from that iron). In agate, sagenite does not refer to a specific mineral (mineralogically, "sagenite" only refers a twinning habit of the mineral rutile) and can be any of several minerals with needle-like or fibrous crystals, including limonite, rutile, calcite, amphibole, etc. Whether rutile or some other mineral, they often grow in acicular (radiating from a central growth point) formations. This can form the substrate on which botryoidal formations grow. In some cases, the sagenite puff, pom pom or dome is a prominent feature in sagenitic agate, while in other cases, the sagenite is only a single needle, or so fine, widely spaced or short that one must look carefully at the walls of the void to detect them. In addition, agate itself has a fibrous structure of stacked crypto-crystals (both in quartzine, lutecite/moganite and length-fast chalcedony) that can form short acicular clusters of needles, leading to botryoidal formations on surfaces. Throw some other forms of quartz into the mix (microquartz, moganite and/or macrocrystaline quartz) and you can get some fascinating structures. So botryoidal formations can form in the absence of sagenite. However, agate is almost never pure silicon dioxide quartz of any variety, and what we call agate seems to form most readily where mineral crystals already exist as a substrate. Addition of other minerals can also give rise to strong colors and optical phenomena (such as fire agate). The Mindat article on chalcedony may be a good starting point for gathering more info. Hi rock2dust, many thanks for this explanation, it helps, well, a little, since most of what you are talking about is beyond my full understanding, I studied industrial engineering, for a living, not Mineralogy, but I do get an appreciation about the formation process. Just as an aside, I had already discovered the Mindat articles which are illuminating, but thanks for sharing anyway. Cheers, johnw  |
|
|
|
Post by johnw on Aug 26, 2018 21:57:07 GMT -5
radial (hemi-spherical) crystallization of the agate makes the domes. This happens with both primate agate bands, and when as a psuedomorph over an existing crystal of another mineral. Banding is often much smaller scale layer of radial hemi-spheres on top of the layer of domes. the basic answer is close together radial spheres or hemi-spheres, and then layers of new agate bands across the Botryoidal surface. This occurs in many minerals. From wikipedia: "Botryoidal minerals form when many nearby nuclei, specks of sand, dust, or other particles, are present. Acicular or fibrous crystals grow radially around the nuclei at the same rate, appearing as spheres. Eventually, these spheres abut or overlap with those that are nearby. These nearby spheres are then fused together to form the botryoidal cluster." Thank you debt123redux for your explanation. So the question becomes over the span of millions of years during the formation process, how can the yellow coloration be confined just to one area and form the "yolk" as it were? The seepage of minerals is prevalent, but yellow seems an odd happening. One more question, where can I find out how crazy lace is mined in the limestone tufts in Chihuahua? Any good reading on this? Cheers, johnw |
|
|
|
Post by Pat on Aug 26, 2018 22:22:49 GMT -5
I want to read the book on how to determine what came first etc in the rock formation. Several of you have read it.
It’s not lithography which I though was a reasonable guess.
What is this study called? Thanks.
|
|
|
|
Post by johnw on Aug 27, 2018 12:20:14 GMT -5
I want to read the book on how to determine what came first etc in the rock formation. Several of you have read it. It’s not lithography which I though was a reasonable guess. What is this study called? Thanks. Hi Pat, Lithography definition is - the process of printing from a plane surface (such as a smooth stone or metal plate) on which the image to be printed is ink-receptive ... Not sure if you are asking, in this egg sample piece, what came first the rock or the egg?  So let me take a stab at it, what came first: Magma. When it cooled it turned to rock, then the rains came and infiltrated the rock and then the egg formed. And so I have solved the proverbial conundrum.......of "What came first".............. the egg came first. The rock was there without form so we cannot definitively say the rock came first. The study of all this is, I think, is called Mineralogy.  Cheers, johnw |
|
|
|
Post by Pat on Aug 27, 2018 13:40:43 GMT -5
I think I need Bonehead Mineralogy with lots of pictures! Thanks.
|
|
|
|
Post by johnw on Aug 27, 2018 17:47:53 GMT -5
I think I need Bonehead Mineralogy with lots of pictures! Thanks. ..............and I thought you were taking the mickey and referring to the chicken and egg question, in a very obtuse way. That said, I do believe I gave an honorable rendition of solving the conundrum........of what came first.  I will stand in line with you waiting for the book. Cheers, johnw |
|
|
|
Post by Pat on Aug 27, 2018 19:41:12 GMT -5
Mini-geomorphology is what I want. It must have a better name! There must be a chapter in the mineralogy book! At this point, I just want the chapter.
|
|
|
|
Post by johnw on Aug 27, 2018 23:04:47 GMT -5
Mini-geomorphology is what I want. It must have a better name! There must be a chapter in the mineralogy book! At this point, I just want the chapter. Hi Pat give this site a try, I just found it, good stuff on Mexican Lace Agate and who knows you may find what you are looking for. Just Google: FMF forum Endomorph or Pseudomorph page 3 What I found fascinating was their pictures of Mex Lace slab samples with structured endomorph and pseudomorph characteristics. Also the pictures of Mex lace vein mining in Chihuahua . Anyway see for yourself and you decide. FMF=Friend of Mineral Forum Cheers, johnw  Follow up on your topic, Google: THE LITTLE BOOK OF GEOMORPHOLOGY:........................its way over my head and I never even got to the mini bit. Cheers, johnw Do I get an "e" for effort? |
|
kskid
Cave Dweller
Member since July 2014
Posts: 98
|
Post by kskid on Aug 27, 2018 23:35:32 GMT -5
I want to read the book on how to determine what came first etc in the rock formation. Several of you have read it. It’s not lithography which I though was a reasonable guess. What is this study called? Thanks. Hi Pat - I think you may have meant lithology (both reference rock  ). As for the study of what came first, would that be stratigraphy? minerken kindly gave me some books that included both of those topics. I don't have the name of the book off the top of my head, but if you're interested I can get it for you. For that matter, I can get you the book when I finish reading it. Let me know. |
|
|
|
Post by Pat on Aug 28, 2018 0:07:49 GMT -5
I want to read the book on how to determine what came first etc in the rock formation. Several of you have read it. It’s not lithography which I though was a reasonable guess. What is this study called? Thanks. Hi Pat - I think you may have meant lithology (both reference rock ). As for the study of what came first, would that be stratigraphy? minerken kindly gave me some books that included both of those topics. I don't have the name of the book off the top of my head, but if you're interested I can get it for you. For that matter, I can get you the book when I finish reading it. Let me know. Yes, lithology makes more sense. I knew lith meant stone. Stratigraphy sounds appropriate. If the books are something that would be an introduction or bone-head level, I might be able to understand them. Yes, I'd like to see them. Thanks. |
|
Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,497
|
Post by Sabre52 on Aug 28, 2018 11:33:31 GMT -5
"The Agates of Northern Mexico" by Brad Cross 1996. Great Book. Got a signed edition in my library and it's one of my favorite agate books.....Mel
|
|
kskid
Cave Dweller
Member since July 2014
Posts: 98
|
Post by kskid on Sept 3, 2018 22:49:22 GMT -5
Hi Pat, I wouldn't call the book Kenny gave me an entry level book. He warned me that these were technical books that assume a fair amount of prior knowledge regarding geology. He wasn't kidding... I've enjoyed reading the stratigraphy book, but I probably only understand about 60% of what's written. I looked for the book online so you could get an idea of the content. I found an online library that will give you access to a digital version for 14 days. Here's the link: Principles of Stratigraphy Disclaimer: I have never used this service, so I can't vouch for it. I'll send you the book if you like. |
|
. Cheers, johnw
I will stand in line with you waiting for the book. Cheers, johnw 
). As for the study of what came first, would that be stratigraphy? 
