It was dusk and I was looking west. A dark object, black, was flying at a high rate of speed about 15000 feet approximately. It was ball or hexagon shaped and had a silver tail behind it possibly from propulsion. The object went directly over my head then disappeared. The sky was totally clear and it vanished into thin air. It was moving about double the speed of a commercial jet. I live next to an airport so i have a frame of reference. It had no lights or sound. Gave me the chills. I cant stop thinking about it.