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Dry sand usually looks homogeneous from even a close distance, but as the photos below illustrate, there is often a wide range of grain sizes and shapes. Getting a representative sample can be difficult: Internal structures (eg., pinstripes, grainflows, and wind ripples), which are hard to see in dry sand, can concentrate grains of particular sizes; much depends on what a subsample happens to include. Then, only a few grains of the sample end up being in a photograph, creating another possible sampling problem. Finally, even a photograph can be misleading, with larger grains covering smaller ones.
'Crumbled Ss' is weathered but intact sandstone rock that was crumbled into sand by gentle finger pressure.
These photos were taken through a hand lens using an inexpensive Canon A570 IS camera (which, importantly, has a lens diameter similar to the human eye), as shown in the photo to the right. The camera was at maximum zoom and in macro mode. Illumination was provided by two halogen worklamps, and colors were coarsely adjusted (semi-systematically) to a white/grey/black reference, using Photoshop. The background was a piece of glossy grey photographic print, where the grey is 93,93,93 (RBG) or 0,0,36 (HSB). Scale was determined by simply photographing a mm scale; the scale on these photos is colour-coded; photos of the same scale have the same colour (eg., all ones with yellow scales are the same scale).
Widening your browser window may display more photos per row, side-by-side.
Also, have a look at a stereogram of Navajo/Page Sandstone sand grains obtained using a macro lens.
