Big black crystal w shiny top panel hovering high over mountain N of Winnemucca noontime Aug '85

It was a barn-sized object twice as wide as tall shaped much like a downward facing lily with about 6 to 8 long and 4 or so short solid smooth black crystal spikes reaching outward and down from its center. It had a car-sized thin silver rectangular panel on top aimed eastward, angled up at about 45 degrees, shining brightly from sunshine.
It "hovered" stationary a thousand or so feet over a long mountain ridge a thousand or so feet tall just a couple miles west of highway 95, around 30 to 45 miles north of Winnemucca Nevada, sometime around noon, on a clear hot dry windy summer day with unlimited visibility on a Sunday in August of 1985.
I watched the target through a 7x monocular from northeast of it for about 5 minutes as a passenger in a van traveling south on highway 95 at about 60-70 mph, paralleling the mountain ridge. When we got as close to it as the highway was going to allow, I still could not identify what the object was even though I was seeing it clearly. Then, after having driven onward 2 or 3 more minutes southeast of the stationary object, it "pixillated" to total invisibility within 2 full seconds of gradually evaporating into thin air.
My observation altogether included those several minutes approaching the closest point the highway got to the object and just a couple or few more minutes continuing past, thus allowing me to see it for quite a while from a wide span of angles before it faded into oblivion.
My stomach sank as it started to pixillate. Inside me I growled "don't you dare disappear before I figure you out"! Then the 2 seconds were up and it was completely gone. I said not a word out loud, however, and never once spoke to anyone of the incident for about 15 years.
The 4 other adults in the van initially acknowledged the obvious black stationary target with shiny top panel in the clear blue cloudless sky, but without magnification they paid it little interest as they enjoyed laughter & conversation on our way home from an adventurous weekend on the last day of the Boise Idaho hot air balloon festival which we had just participated in. I haven't yet been able to nail down what exact date that was to the day.
I was awake and sharp as ever during my sighting. I had been involved extensively in hot air ballooning for half a decade up till then and nearly a decade since, so have had my eye in the sky observing flying machines quite a bit. The bulky, big black crystal's rock-solid stationary stability during my 7 or more minutes total observation seemed impossible on such a windy day. Its disappearing act was especially confounding.
Witness indicates that the date of the incident is approximate.  PD