I was the Legal Svcs Chief at MCAGCC, 29 Palms and just left the Marines. I was a at local park late at night with a friend. We were laying down in the back of my SUV when I noticed an object just above us moving slowly with a very low hum. The lights reflecting in the park just made it noticeable and I jumped up and grabbed my mag-light and pointed at the object. It's surface was a dull black or dark grey color that did not reflect my light back or had lights or windows. The shape was triangular with a slight boomerang indent in the back. My friend also noticed the object and did not understand what we where looking at, but was confused and a little unnerved. I was just transfixed on the object and extremely interested in following it, which I did until I hit Hwy 62, at which point I could no longer follow it and lost it going in the same direction until I lost it over the Joshua Tree National Park. The entire event lasted approximately 15-20 minutes. The object was large at about 50-100 feet across, and about 100+ Feet above us.