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Geology/Geology rock description


While checking rock cutting samples (under microscope) is it technically correct to say that a "CLAYSTONE is grading to SILTY CLAYSTONE".

The rock is primarily a Claystone which is silty in places

or should it be CLAYSTONE grading from a SILTY CLAYSTONE.

Usually a rock chip on a thin section is hardly of 0.5x0.5 cm, so it would not be wise to say "one rock is grading into another.
Lateral and vertical heterogeneity within a rock can be quite variable to use  such a liberty.

You have to see whether the rock is predominantly a claystone or a siltstone and this situation can be laterally or vertically as well.

A siltstone can have clay rich lavers  and vice versa.


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