I was on my lunch break walking north, when a light gray shape caught my eye. the object was approximately 500 feet away, about 50 feet in the air over a building. at first i thought it was a flock of birds, and i said, that's interesting, what kind of birds would those be? it seemed to be moving east in a slow flutter. then it disappeared, like it folded back into the sky. at this point, i said, well that's strange. it then reappeared in a fat boomerang shape. it seemed to be made up of multiple light gray, possibly reflective objects but working together, like a school of fish, or sequins on a purse or dress. it did seem to have a common background that was dark gray or black. it was still fluttering, but it paused and hovered and moved backward, just slightly. at this point, i have a bare tree in my way, but i am still walking, so i was past it quickly. when i saw the shape again, it had changed, and it seemed to be a soft, billowy, upside down parachute shape, or the bottom of a puffy cloud or a puff of factory smoke. i almost convinced myself it was a deflated weather balloon, but there was no top to the shape, only a distinct bottom. the color of this object seemed to blend with the sky, i could only decipher a dark gray sitting in the bottom of the cloud/parachute. then the object changed again, and became almost transparent, as if the sun were reflecting on an invisible craft. now there really is no overall shape that i can make out. i saw a few smaller very rigid shapes, like flat prisms or solar panels, and they seemed to fold backwards into the object and then the whole object faded away. this all transpired in about 20 - 25 seconds. at this point, another sparse tree is blocking my view. i assumed the object would reappear, as it already had, so i said to myself, i will take a picture with my phone when i get to the other side of the tree, but it never appeared again. i looked for it for about 6 more minutes, but saw no sign of it. the object made no sound during this encounter. the other objects in the sky were two passenger planes flying east almost parallel to each other, but they were a miles away. there was a helicopter about 10 miles east circling. there is also a military base close by, and planes are frequently seen. a military cargo plane flew over a few minutes later. additionally, a cv-22 osprey plane flew over a few minutes after the first military plane. i do not know if it lingered in the vicinity, as i had to go back to work. of note, the building i believe the object was moving over, processes precious metals.