The Sandbow

Several writers in the 19th century, including Florence Nightingale, recorded their impressions of a rainbow-like phenomenon seen in the desert, and assumed to be caused, not by droplets of rain, but by grains of sand. Is it, in fact, possible for spherical grains of sand to exist in a great enough quantity for thisd, for the relatively heavy sand to be lofted into the air, and to be transparent enough to produce what we have to call a “sandbow”? Speculation centered around “oolitic” sand that nucleates around organic matter and is naturally rounded, but which is translucent, rather than transparent.