Rocky Posted July 10, 2017 Share Posted July 10, 2017 Hi guys and gals, I found this today and what grabbed my attention was the exterior had the appearance of contractions but I'm really not sure what to think. It attracts a magnet, feels dense for its size. It's 65gr, approximately 2"x1-9/16"x1". I opened a window and polished to 600 and there are no chondrules, but I do see those lines within the matrix. I guess what I mostly would like to know is that in the likelihood that this is terrestrial, what are the tell tail signs seen under magnification like a magnify glass strength or loop that can help one positively identify shock veins apart from just ordinary cracks filled with minerals washed in. Quote Link to comment Share on other sites More sharing options...
Mikestang Posted July 10, 2017 Share Posted July 10, 2017 (edited) If it were a chondrite you would see metal flecks in the polished window. It appears to be terrestrial to me. Contraction cracks occur in the fusion crust as it cools rapidly, they don't "crack" all the way into the stone beneath, such as you see here. Shock veins are veins of shock melt, it appears that physical cracks are visible in your window. Good pictures, keep looking. Edited July 10, 2017 by Mikestang 1 Quote Link to comment Share on other sites More sharing options...
Rocky Posted July 10, 2017 Author Share Posted July 10, 2017 Thanks Mike, I'm glad you clarified the contractions part because I was under the impression surface tension from the rapid cooling could cause ~some~ fracturing beneath the surface as well apart from just the fusion crust contracting, not thoroughly of course. Quote Link to comment Share on other sites More sharing options...
Rocky Posted July 10, 2017 Author Share Posted July 10, 2017 My Al Haggounia on the other hand has clear examples of shock melt veins and a nice NWA I have has awesome shock veins almost 2mm in some parts!!! I Love these ones. Quote Link to comment Share on other sites More sharing options...
Nugget Shooter Posted July 10, 2017 Share Posted July 10, 2017 What did a streak test tell you Rocky? Grey/black? Quote Link to comment Share on other sites More sharing options...
Rocky Posted July 10, 2017 Author Share Posted July 10, 2017 (edited) 35 minutes ago, Bill Southern said: What did a streak test tell you Rocky? Grey/black? It was Grey. Edited July 10, 2017 by Rocky Quote Link to comment Share on other sites More sharing options...
Rocky Posted July 10, 2017 Author Share Posted July 10, 2017 Perhaps greyish brownish. Little bit of both. Quote Link to comment Share on other sites More sharing options...
Nugget Shooter Posted July 11, 2017 Share Posted July 11, 2017 Magnetite likely.... Quote Link to comment Share on other sites More sharing options...
Rocky Posted July 11, 2017 Author Share Posted July 11, 2017 6 minutes ago, Bill Southern said: Magnetite likely.... Well on to the next....?, thanks Bill !! 1 Quote Link to comment Share on other sites More sharing options...
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