sandstone - arkosic fine grained sandstone - UNIT OF 5 STUDENT SPECIMENS

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Fine-grained arkosic sandstone - Unit of 5 teaching student specimens from Upper Miocene Cajon Valley Formation
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.
You are buying a unit of five student specimens.
The photo is representative of what we ship.
For teachers we count like a baker and a dozen is more than 12, since you will always need a few spares. If you are a teacher, say so by using the "ask a Question" link below.
We object to students being given tiny fingernail-sized specimens to study, but realize that this happens because of cost. We much prefer that students work with specimens 2" or larger, where the mineral's or rock's characteristics are easier to see, and we price them low enough that a classroom set becomes affordable. We want the "Oh, Wow!" effect when students see the set of specimens they are going to work with.
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