Dear Mr. Shan,

I assume that you speak about consolidated material and siliciclastic sedimentary rocks. In this case every disintegration either mechanical or chemical will impact on the grain size and grain morphology which you should always have a look at together. There may be some way out of the dilemma by making use of polished sections under the SEM/EDX-WDX. The method is not very much different from what you can also apply to polished thin sections. From whatever angle you may look at the problem any manipulation will in one or the other way bias your results.

Good luck !

H.G.Dill

Thin section method is the method applied for such type of hard and consolidated sandstone for their grain size analysis. You prepare alteast two to three polished thin section from different sides of the grab samples, do grain size measurement for atleast 300-500 grains which will give you better representation of its modal percentage.

The answer depends on whether you want to do it in the field or in the lab. Semi-quantitatively you can do a grain size analysis in the field of loose proximally weather material. The lab is easier. You can use tomography that is usually applied in medicine, although it is becoming more common in other fields, but you can also use XRD with an unpowdered sample. The granularity of the XRD pattern is a function of grain size. We developed a method of doing this for planetary exploration. Would be happy to provide more info if you would like.

The bottom line is that there is NO standard methodology. Which ever method you apply would require an immense amount of work to calibrate the technique. If you have to do it in field, your best bet is to literally "feel" the surface roughness and use a good magnifying glass.

Cheers,

John.