Sand Photomicrographs

Jan 2004

How do sand grains from pinstripes compare with grains from between pinstripes?

Navajo Sandstone (Paw Hole)

The photo to the right shows where sandstone was sampled. The pinstripe material was obtained by breaking off a small piece (less than 1 square centimeter) of the 1mm-thick 'wafer' protrusion visible in the photo and then gently crushing it between two sheets of paper with slight finger pressure. 'Between pinstripe' grains were obtained by rubbing the 'interstripe' area shown in the photo and collecting the falling grains.

(Click on the photo for an enlargement.)

Below are photomicrographs of the sand grains from each source.

Pinstripe grains

Grainflow grains

Paw Hole Dune Sand

Dune sand was obtained from the same area, presumably eroded from the surrounding sandstone. A small amount was sorted by heaping a well-mixed sample upon a piece of paper, and then shaking off the large particles (right photo below), leaving the smaller particles (left photo below).

The large dune grains don't have the 'frosting' that is visible on the large grains from the sandstone. The frosting might be traces of material that held the grains within the sandstone, which weathered off the dune grains.

These photomicrographs were produced using an Intel QX3. The sand grains were resting on a black transparency (photographic slide) and top-lit from an oblique angle.