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Gemstones, Minerals & Fossils
Fossils
Graphtolite fossils in slate
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<blockquote data-quote="user 4386" data-source="post: 417095" data-attributes="member: 4386"><p>No, you are quite right - pyrite. Common in carbon-rich slate. You can reduce your work finding graps if you just split slates where the cleavage (that it splits along) is parallel to the bedding. So on the limbs of folds not in the axis. Your bottom slabs are like that, but the top one would be a dead loss. You can see from the colour banding on the cleavage plane it has split along that the cleavage is not parallel to bedding, but cuts through multiple beds. Graptolites were deposited in the plane of bedding (cleavage came later when the rocks were folded) - so cleavage needs to be parallel to bedding.</p><p></p><p><a href="https://courses.eas.ualberta.ca/eas421/images/foldpiccleavage3d.jpg" target="_blank">https://courses.eas.ualberta.ca/eas421/images/foldpiccleavage3d.jpg</a></p><p></p><p><a href="http://www.geosci.usyd.edu.au/users/prey/FieldTrips/BrokenHillOlary/Images/Fold2b.jpg" target="_blank">http://www.geosci.usyd.edu.au/users/prey/FieldTrips/BrokenHillOlary/Images/Fold2b.jpg</a></p></blockquote><p></p>
[QUOTE="user 4386, post: 417095, member: 4386"] No, you are quite right - pyrite. Common in carbon-rich slate. You can reduce your work finding graps if you just split slates where the cleavage (that it splits along) is parallel to the bedding. So on the limbs of folds not in the axis. Your bottom slabs are like that, but the top one would be a dead loss. You can see from the colour banding on the cleavage plane it has split along that the cleavage is not parallel to bedding, but cuts through multiple beds. Graptolites were deposited in the plane of bedding (cleavage came later when the rocks were folded) - so cleavage needs to be parallel to bedding. [url]https://courses.eas.ualberta.ca/eas421/images/foldpiccleavage3d.jpg[/url] [url]http://www.geosci.usyd.edu.au/users/prey/FieldTrips/BrokenHillOlary/Images/Fold2b.jpg[/url] [/QUOTE]
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Gemstones, Minerals & Fossils
Fossils
Graphtolite fossils in slate
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