Black Triangle Sighting in Jefferson, Oregon on June 13th 2015 – 1/2 acre wide X20 ft tall dark gray gunmetal colored hovering Triangle craft

Went outside just as getting dark, looked up and saw large dark gray gunmetal colored triangle craft of huge size aprox 1/2 acre wide X 20 ft tall hovering over my property. It made absolutely no sound nor did it have any lights, I looked away momentarily questioning what I had just seen, in all of about 4 seconds time when I looked up it completely disappeared without a sound. I wish to remain anonymous. I had the impression this was a military craft of immense size and capabilities.