The non-reflective spheres could be of extra-terrestrial origin, but most likely they are oxidized (rusted) spheres from human activity blown in from who knows when or where.
Some more photos:
(Photo 2.) Spheres with metallic debris. (200x)
(Photo 3) Approximately 100 spheres gathered from about a two square yard surface area at nearby recreational area. A portion of panorama from 200x images which could have been obtained with a 30x to 50x lens. (Human hair with diameter of about 100 microns used as reference.)
I have many other photos from samples gathered from three other locations, all within 3 miles, so this is not an isolated contamination location, depending on your definition of "isolated".
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Doing it yourself -
(1) - Get a relatively strong magnet.
(2) - Cover the magnet with a plastic bag (or else the particles will be difficult to remove from the magnet).
(3) - Drag the magnet over the ground that is exposed to the open sky. Natural drain points, such as the debris from drain spouts works quite well. In a few minutes' time you will get lots of debris, iron-containing rocks and rusty metal bits from time past, as well as hopefully a micrometeorite, but highly probable, some of these spheres.
(4) - Clean the gathered material with gently flowing water and dry.
(5) - Heat slowly to remove moisture and to demagnetize the metallic material.
(6) - View under a 50-200x microscope lens.
See Photo 2 above with magnetized metallic debris.
