7/20/91, 1630, Sierra Vista AZ, 2 to 3 minutes, flattened egg, matte black, observed by myself

It was an inky black, flattened egg-shape with no surface detail, no sound, height and size unknown.  The weather was overcast with scudding clouds and mist over the nearby Huachuca Mountains (maximum elevation is at Miller's Peak, 9,465 feet); latitude 31.33N, longitude 110.18W; wind aloft WNW.  While looking at dark clouds and lightning to the north, I at first mistook the object for a large bird flying towards me head-on, and then as a balloon.
The object disappeared into the mist before Miller's Peak as I observed from a lower elevation, approximately 4,700 feet.  The unknown was moving from East to West at an even speed in a straight flight path.
There are animal mutilation reports that occurred in at least three counties in southeast Arizona (Cochise and Santa Cruz) that overlapped my sighting.