I was working at the Mecco mine near London Mills, IL on 10/05/68. Fall was dry so need for pumps in the strip mine after a rain was nill, but pumps needed to be maintained. My detail from the shop of 6 men including me went towed in 3 pumps that needed to be oiled and lubed up. We were driving down the pit when one of the guys noticed the german wheel excavator had stopped digging, its lights got real dim as we appeared over the rim. Our two way radio did notwork, all there was static. Another man noticed a disc with an orange halo around it. It was moving real slow. Me and my crew was scared and tried to call the whhel shovel but all we got was static, 4 hours would be the shift change. At shift change, the drivrr noticed an unusual lighted object that came closer to the german wheel excavator. it was disc about 50-100 ft across and domed tounded on top. Very creepy, it then disappeared. We drove by a relay station (pwer booster station). Something had blown out, could smell it.