sandstone - arkosic fine grained sandstone - teaching hand/display specimen

Description

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Fine-grained arkosic sandstone - teaching hand/display specimen
This fine grained sandstone is surprisingly an arkose, which means that a large percentage of the sand grains are feldspar. It is a bright and clean sandstone, not the coarse grained rusty arkose we visualize as typical. The flat cleavage surfaces of the feldspar grains are clearly visible under 20x magnification. Under a 10x hand lens, these sparkle when the specimens are tilted back and forth.
This is a useful example of a fine-grained sandstone, and most students will see it as that. An advanced student of geology might pick it out as an arkose. It is Upper Miocene in age, from the Cajon Valley Formation, terrestrial in origin. The cement is silica, so there is no effervescence with a drop of hydrochloric acid.
The sand grains in these specimens are larger than those of a silt and will feel and look like fine sand to a student. It would be instructive to compare this sandstone with one is larger grained, with one that is cemented with calcium carbonate, and with different colored sandstones, as sandstone has great variety and a student should not see only one example.
These specimens will fit into a 3.5” x 5.25" specimen tray. We include data with every specimen: collecting locality for minerals and rocks and also the formation and age, if determined. These are slightly thicker than hand specimens, but otherwise the same, and would best be purchased with other specimens, which can ride in the  same box.
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You can select a specimen by telling us what is in front of it - a black mechanical pencil, a silver and black pen, a silver and blue pen, or one of those plus some number of coins, or you can let us make the selection.
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