Comments for Sandatlas http://www.sandatlas.org Wed, 22 Feb 2012 12:59:18 +0200 hourly 1 http://wordpress.org/?v=3.3.1 Comment on What is sand made of by daniele martinelli http://www.sandatlas.org/2011/10/what-is-sand-made-of/#comment-185 daniele martinelli Wed, 22 Feb 2012 12:59:18 +0000 http://www.sandatlas.org/?p=1374#comment-185 I am a sand collector from Italy My collection of over 6,000 samples. I have much material to change. Are you interested in doing an exchange? Best regards. Daniele Martinelli Ravenna - Italy I am a sand collector from Italy
My collection of over 6,000 samples. I have much material to change. Are you interested in doing an exchange?
Best regards.

Daniele Martinelli
Ravenna – Italy

]]> Comment on Pillow basalt more than a kilometer above sea level by Hollis http://www.sandatlas.org/2012/02/pillow-basalt-more-than-a-kilometer-above-sea-level/#comment-183 Hollis Tue, 21 Feb 2012 00:18:02 +0000 http://www.sandatlas.org/?p=4756#comment-183 Really neat looking, especially with the moss accentuating the circular patterns (photo with you). Really neat looking, especially with the moss accentuating the circular patterns (photo with you).

]]> Comment on Pillow basalt more than a kilometer above sea level by Ron Schott http://www.sandatlas.org/2012/02/pillow-basalt-more-than-a-kilometer-above-sea-level/#comment-182 Ron Schott Mon, 20 Feb 2012 23:10:30 +0000 http://www.sandatlas.org/?p=4756#comment-182 I also concur with Callan's assessment. I also concur with Callan’s assessment.

]]> Comment on Pillow basalt more than a kilometer above sea level by Lockwood http://www.sandatlas.org/2012/02/pillow-basalt-more-than-a-kilometer-above-sea-level/#comment-181 Lockwood Mon, 20 Feb 2012 20:00:20 +0000 http://www.sandatlas.org/?p=4756#comment-181 I agree with Callan- this looks much more like sphereoidal weathering than pillow basalt. I agree with Callan- this looks much more like sphereoidal weathering than pillow basalt.

]]> Comment on Pillow basalt more than a kilometer above sea level by Callan Bentley http://www.sandatlas.org/2012/02/pillow-basalt-more-than-a-kilometer-above-sea-level/#comment-180 Callan Bentley Mon, 20 Feb 2012 19:41:36 +0000 http://www.sandatlas.org/?p=4756#comment-180 That looks just like spheroidal weathering of basalt to me. Like the one at the end of this post: http://nvcc.edu/home/cbentley/geoblog/2008/01/columnar-jointing-and-weathering.html I don't see the radial fractures I associate with pillows, or the textural zonation of pillow interior vs. flash-frozen "crust." The onion-skin style sheeting seems more consistent with spheroidal weathering than a pillow basalt origin. And lastly, it seems that these shapes are strongly controlled by the vertical and gently-dipping joint sets. That looks just like spheroidal weathering of basalt to me. Like the one at the end of this post:
http://nvcc.edu/home/cbentley/geoblog/2008/01/columnar-jointing-and-weathering.html
I don’t see the radial fractures I associate with pillows, or the textural zonation of pillow interior vs. flash-frozen “crust.” The onion-skin style sheeting seems more consistent with spheroidal weathering than a pillow basalt origin. And lastly, it seems that these shapes are strongly controlled by the vertical and gently-dipping joint sets.

]]> Comment on Dunite xenolith by Siim http://www.sandatlas.org/2012/02/dunite-xenolith/#comment-176 Siim Sun, 19 Feb 2012 18:19:20 +0000 http://www.sandatlas.org/?p=4692#comment-176 Ron, thanks for explaining this. I was also inclined to interprete it as you did. Ron, thanks for explaining this. I was also inclined to interprete it as you did.

]]> Comment on Dunite xenolith by Ron Schott http://www.sandatlas.org/2012/02/dunite-xenolith/#comment-175 Ron Schott Sat, 18 Feb 2012 23:01:27 +0000 http://www.sandatlas.org/?p=4692#comment-175 In my estimation you could safely call this a dunite xenolith. Dunite is defined simply as an ultramafic plutonic rock containing >90% olivine. Xenolith means literally "foreign rock" and implies a rock sample that did not originate from the magma in which it ended up. As this sample is most likely a piece of the mantle or lower crust broken off as the basaltic magma ascended it is entirely proper to call it a xenolith. However, one should be cautious not to use the term xenolith for just any inclusion in a crystallized magma body. Sometimes enclaves (a more generic term for inclusions) can be composed of earlier crystallized portions of the same magma chamber they are later incorporated into. A fair amount of fine grained "mafic" enclaves in granitoids are actually cogenetic with the rock in which they are included. I think the following quote from Wikipedia accurately sums up my understanding of the proper usage: "To be considered a true xenolith, the included rock must be identifiably different from the rock in which it is enveloped; an included rock of similar type is called an autolith or a cognate inclusion." (http://en.wikipedia.org/wiki/Autolith) In my estimation you could safely call this a dunite xenolith. Dunite is defined simply as an ultramafic plutonic rock containing >90% olivine. Xenolith means literally “foreign rock” and implies a rock sample that did not originate from the magma in which it ended up. As this sample is most likely a piece of the mantle or lower crust broken off as the basaltic magma ascended it is entirely proper to call it a xenolith. However, one should be cautious not to use the term xenolith for just any inclusion in a crystallized magma body. Sometimes enclaves (a more generic term for inclusions) can be composed of earlier crystallized portions of the same magma chamber they are later incorporated into. A fair amount of fine grained “mafic” enclaves in granitoids are actually cogenetic with the rock in which they are included. I think the following quote from Wikipedia accurately sums up my understanding of the proper usage: “To be considered a true xenolith, the included rock must be identifiably different from the rock in which it is enveloped; an included rock of similar type is called an autolith or a cognate inclusion.” (http://en.wikipedia.org/wiki/Autolith)

]]> Comment on Dunite xenolith by Xenobombs on the Half Shell » Ron Schott's Geology Home Companion Blog http://www.sandatlas.org/2012/02/dunite-xenolith/#comment-174 Xenobombs on the Half Shell » Ron Schott's Geology Home Companion Blog Sat, 18 Feb 2012 22:19:40 +0000 http://www.sandatlas.org/?p=4692#comment-174 [...] so uncommon as they might at first seem – indeed, Siim Sepp at Sandatlas proceeded to produce his own sample from Lanzarote in the Canary Islands. In fact, I’ve collected samples like this at Kilbourne Hole in New [...] [...] so uncommon as they might at first seem – indeed, Siim Sepp at Sandatlas proceeded to produce his own sample from Lanzarote in the Canary Islands. In fact, I’ve collected samples like this at Kilbourne Hole in New [...]

]]> Comment on Dunite xenolith by Felix Bossert http://www.sandatlas.org/2012/02/dunite-xenolith/#comment-173 Felix Bossert Sat, 18 Feb 2012 20:51:26 +0000 http://www.sandatlas.org/?p=4692#comment-173 http://1.bp.blogspot.com/-XQ2ADcTS9SM/T0ANYM1qR7I/AAAAAAAAAO8/DkBX8cyNUS0/s0/XenolithOrDuniteFromCanaryIslands.jpg http://1.bp.blogspot.com/-XQ2ADcTS9SM/T0ANYM1qR7I/AAAAAAAAAO8/DkBX8cyNUS0/s0/XenolithOrDuniteFromCanaryIslands.jpg

]]> Comment on Dunite xenolith by Felix Bossert http://www.sandatlas.org/2012/02/dunite-xenolith/#comment-172 Felix Bossert Sat, 18 Feb 2012 20:50:46 +0000 http://www.sandatlas.org/?p=4692#comment-172 link to picture: <a href='http://1.bp.blogspot.com/-XQ2ADcTS9SM/T0ANYM1qR7I/AAAAAAAAAO8/DkBX8cyNUS0/s0/XenolithOrDuniteFromCanaryIslands.jpg' rel="nofollow">here</a> link to picture:

here

]]> Comment on Dunite xenolith by Felix Bossert http://www.sandatlas.org/2012/02/dunite-xenolith/#comment-171 Felix Bossert Sat, 18 Feb 2012 20:49:53 +0000 http://www.sandatlas.org/?p=4692#comment-171 Thanks for your explanations. Now I know what the star of my stone collection ( <a href='http://1.bp.blogspot.com/-XQ2ADcTS9SM/T0ANYM1qR7I/AAAAAAAAAO8/DkBX8cyNUS0/s0/XenolithOrDuniteFromCanaryIslands.jpg' rel="nofollow">here</a> . Thanks for your explanations. Now I know what the star of my stone collection (
here .

]]> Comment on Houses built from diamonds and impact breccia by Diamonds Other Gems Reis http://www.sandatlas.org/2012/01/houses-built-from-diamonds-and-impact-breccia/#comment-170 Diamonds Other Gems Reis Fri, 17 Feb 2012 03:44:03 +0000 http://www.sandatlas.org/?p=4037#comment-170 [...] [...] [...] [...]

]]> Comment on Gigapans of sand by Siim http://www.sandatlas.org/2012/02/gigapans-of-sand/#comment-166 Siim Mon, 13 Feb 2012 19:45:26 +0000 http://www.sandatlas.org/?p=4610#comment-166 There are many interesting minerals. I do not want to name them before I am sure. I should use microprobe or something similar for this but it is not possible during the next month or two. There are many interesting minerals. I do not want to name them before I am sure. I should use microprobe or something similar for this but it is not possible during the next month or two.

]]> Comment on Gigapans of sand by kate http://www.sandatlas.org/2012/02/gigapans-of-sand/#comment-165 kate Mon, 13 Feb 2012 03:01:24 +0000 http://www.sandatlas.org/?p=4610#comment-165 These are impressive! The Le Paree sand is pretty with all the garnets. One can see remarkable details in the grains. I'd love to know the magnification as I zoom in and out. There's a bottle-glass green grain at about 10:30, a quarter in from the edge. Is this glass, jade, epidote? Actually, looking further, I see more of this color. Maybe some zircons too. Fun to see what this technology can show with sand. Thanks for sharing! These are impressive! The Le Paree sand is pretty with all the garnets. One can see remarkable details in the grains. I’d love to know the magnification as I zoom in and out. There’s a bottle-glass green grain at about 10:30, a quarter in from the edge. Is this glass, jade, epidote? Actually, looking further, I see more of this color. Maybe some zircons too. Fun to see what this technology can show with sand. Thanks for sharing!

]]> Comment on Dunite by Siim http://www.sandatlas.org/2012/02/dunite/#comment-164 Siim Sun, 12 Feb 2012 17:22:17 +0000 http://www.sandatlas.org/?p=4623#comment-164 Yes, it is likely. This rock sample doesn't belong to me. I took that photo few days ago but I can not examine the sample at the moment. This rock belongs to my university. It was collected by an amateur geologist who just gave his whole collection (7 tons of rocks!) away few years before he passed away (I will write a post about him soon). There are many wonderful samples but unfortunately they are mostly poorly described or not at all. I am destined to make lots of mistakes but I hope that fellow geologists help when they spot possible errors. I am currently taking photos of these samples. This is huge amount of work and I really do not spend much time to study them in detail. I just take the samples out of plastic bags where they are stored, take photos of the best samples and quickly move on. I think your interpretation is probably true. This is only good because I really do not have a photo of lherzolite yet :) I will add your picture of fresh dunite to the article also. Yes, it is likely. This rock sample doesn’t belong to me. I took that photo few days ago but I can not examine the sample at the moment. This rock belongs to my university. It was collected by an amateur geologist who just gave his whole collection (7 tons of rocks!) away few years before he passed away (I will write a post about him soon). There are many wonderful samples but unfortunately they are mostly poorly described or not at all. I am destined to make lots of mistakes but I hope that fellow geologists help when they spot possible errors. I am currently taking photos of these samples. This is huge amount of work and I really do not spend much time to study them in detail. I just take the samples out of plastic bags where they are stored, take photos of the best samples and quickly move on. I think your interpretation is probably true. This is only good because I really do not have a photo of lherzolite yet :) I will add your picture of fresh dunite to the article also.

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