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Post by snowmom on May 22, 2015 5:56:41 GMT -5
A while back after Jamesp posted photos of the impactite and other rocks I sent him, I sent a box of similar material to Fantastic5 (Ann). We had been kicking around identity of some of the stuff found here and all of us having curious minds were hoping to find IDs of some of those rocks. Ann cut samples and took them to a friend and colleague, Wayne, who is a geologist by profession. Wayne took the time when not involved in his professional pursuits to prepare slides and samples for examination and Ann got to see them examined and hear them explained. She took copious notes and they sent me an analysis of 9 different samples. 3 of them were impactite, and the others had surprises. The first to be examined was this one : forum.rocktumblinghobby.com/thread/68871/red-green-mystery
Quoting the report : Amygdaloidal basalt- fine magnetite rich matrix filled with small plagioclase crystals. voids are filled with epidote, chalcedony and jasper.
I am going to make several separate posts to this thread as I have tried to make one long post a couple of times and lost it all due to a misplaced finger on the keyboard. more to follow
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Post by snowmom on May 22, 2015 6:38:16 GMT -5
second, fifth and seventh samples were all impactites, my surmise is that they are all from Sudbury impact event, since the impact site is 150 miles away directly across Lake Huron and I have found many Black Onaping pieces locally. Some of the quartz in the impactites had bubbles or had flow lines and also showed that it picked up debris while still soft/liquid.(inclusions). It is my understanding that Wayne was delighted to find shocked quartz as well, and to have a sample of it in hand. showing quartz with inclusions Shocked quartz showing fracture lines where the shock waves of impact have shattered the crystal. I have to stop posting for the moment, more good stuff to follow. I am so grateful to Ann and to Wayne for all the time invested and the trouble they have gone to in making this information available to me. There are just incalculable hours of preparation, photo taking, video making, report preparation, consultation, analysis and so much more invested here. I will be looking at photos and videos and reading and trying to understand everything in all of it for a long time. Great material for study. You both have given me an unparalleled learning opportunity and I deeply appreciate all your time and trouble. There is no way to express my gratitude, and the tremendous excitement of having all of this information at hand. Thank you so very much!
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Post by snowmom on May 22, 2015 6:39:14 GMT -5
PS Ann and Wayne, if I have made an error in reporting, please correct me!
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Post by snowmom on May 23, 2015 5:01:22 GMT -5
This was an interesting one, we come across quite a bit of it, with the bits embedded in it, I always thought of it as some sort of conglomerate. quoting the report again: #3 Highly metamorphosed siltstone "semi schist"- the sample is highly fragmented with relic bedding seen within the broken fragments. Highly quartzose fragments are surrounded by abundant chlorite mica. Lots of secondary pyrite speckles the entire sample. Iron Oxide staining within the fractures is evident. Occasional fragments of very coarse and very fine quartzite material are seen.
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Post by snowmom on May 23, 2015 5:06:07 GMT -5
I love this stuff. I find it all over and have a hard time resisting it. it seems to come in gray and green base colors but that could be surface staining. quoting again. Sample 4 _ Conglomerate- sub rounded to angular fragments are seen suspended in a finer matrix. Fragments consist of quartzite, granite and basalt. Plagioclase and orthoclase are both noted in large pieces along with quartz and the rare biotite grain here and there. Some of the quartzite fragments contain sericite mica. Several garnets were noted along with secondary pyrite filling the cracks and voids.
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Post by snowmom on May 23, 2015 5:11:53 GMT -5
sample 6. beginning to notice a theme, it seems most of the things I pick up are metamorphic. quoting : sample 6- Metasedimentary Greenstone- Silt to clay size quartz grained rock. Fragmented pieces are filled and surrounded by chlorite. Minor amounts of augite are seen. There is secondary pyrite noted in small amounts. Larger sections of quartz show welded margins, secondary overgrowth and fracture filling, indicating possible low temperature hydrothermal alterations.
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Post by snowmom on May 23, 2015 5:34:10 GMT -5
Also noted that pyrite seems to infiltrate or be included in almost everything here! One of the biggest informers for me was that the nuggets and particles that I thought must be nickel/iron in the impactites and in other rocks turned out to be pyrite. I knew pyrite was common in this area. No nickel/iron was found in any of the samples. Sample 8 was the biggest surprise by far. quoting report Sample 8- Dense chlorite or Chlorastrolite - This sample appears to be a low pressure hydrothermally altered gabbro. This metamorphosed gabbro shows all its pyroxene crystals have been altered to very fibrous grains of actinolite. Actinolite grains are very dense but only show minimal compaction. this microscopic photo clearly shows the actinolite "tail" developed from the pyroxene crystals. now commenting, not quoting. Wayne thought this was on its way to becoming chlorastrolite- but not quite arrived at those changes, but borderline.
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Post by snowmom on May 23, 2015 5:57:13 GMT -5
Sample 9 was epidosite- quoting: sample #9- Epidosite- epidote grains intermixed with hydrothermally welded quartz grains . Ann says it was the densest/heaviest of the samples they looked at. If I remember correctly it looked similar to Wampidy's picture in this thread. But do I remember correctly? forum.rocktumblinghobby.com/thread/68838/unakite-epidote-lake-superiorI still have lots of notes and photos/videos to sort through and there is a load of information yet to be added for a complete report on each specimen. I will be working through it and adding more information as I make sense of it and am able to in time. That's it for now. Thanks for looking. Thanks again to Ann and Wayne for giving of their time and effort so generously to gather all the information and make it available to me. I am learning more each time I go through the notes and pictures/videos. So grateful for this opportunity, what a blessing! comments and corrections welcome!
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Post by mohs on May 26, 2015 20:21:04 GMT -5
so is that pulverized rock that was used for the microscopy ?
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Post by snowmom on May 27, 2015 6:16:29 GMT -5
yes, thin slices and powdered rock from each sample was used for diffraction studies and microscope. Ann fantastic5 could tell you more- she was there!
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Post by fantastic5 on May 27, 2015 12:47:12 GMT -5
so is that pulverized rock that was used for the microscopy ? The pulverized rock was used in the x-ray diffractometer. Picture of the actual instrument below. That is how the complete elemental analysis of the material was made. The thin sections for the microscopy are really incredible. I didn't take a picture of the machine that makes the thin section. But I found a generic video that describes the process. Waynes was bigger . This was clearly the most time consuming piece of the analysis. Even after the thin sections were created each slide took a prolonged period of time hand grinding with grit on a thick plate of glass until the material was thin enough to transmit light. I am really amazed at the amount of time that went into each thin section slide. And Wayne made 9 of these for Deb and myself! Again, pictures pilfered from the web, but this really does show how the block of stone gets ground all the way down to a thin section that can transmit light. Yes, the rock is attached to the slide! The only material that we looked at that would not transmit light was pyrite and hematite. Wayne would use a flashlight to illuminate the top of those pieces while viewing microscopically (both with polarized and plain light) to determine composition. It is a talent for sure. I can read a human blood smear in my sleep and tell you what sort of genetic diseases or cancers the person has. Wayne can read the geological thin sections with the same ease. I found it amazing!
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Post by mohs on May 27, 2015 20:35:07 GMT -5
That GeoForm machine is crazy cool I never seen one & I want one !
A vacuum pump to dop lots of possibilities there!
Whole lot easier than the old days of hand lapping a slice of stone to get it thin enough to transmit light
You must be working a in a lab with all those magical centrifuging machines. The way they can get bio-fluids to separates their secrets Simply amazing technology!
Thanks so much for posting
Ed
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