shale - hard gray Silurian shale from the Inyo Mountains of California - unit of 5 student specimens
This hard gray Silurian shale outcrops at 8,200' in Mazourka Canyon in the Inyo Range, Inyo County, California, speaking to the amount of uplift in that range. It is very slightly limy and gives a very weak effervescence, if any, with hydrochloric acid.
Students should know the basic sedimentary rocks in order of increasing grain size, from mudstone and shale, siltstone, sandstone to conglomerate and coquina.
Shales differ from mudstones in that they are more compressed, form flat plates, and are less likely to disappear in a poof of dust when dropped by a student. This shale is fairly hard and should stand up to student examinations.
Some shales closely resemble slate, metamorphosed from shale. To distinguish a shale from a slate, the field test is to lick it. The shale will smell muddy. The slate won't. This shale passes the lick-and-sniff test and smells distinctly muddy.
The field photo shows how this shale weathers out in large clinky plates. On slopes it forms the many small chips typical of shale weathering.
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