Excavator was producing material from pit floor in front of lower bench of highwall. For unknown reason highwall gave way & material made contact w/ excavator & cab. Material entered cab & EE received cut above lt eye at hairline on scalp. EE was taken to ER for check up & 1st Aid on Cut. On 9/21/20 EE went back for x-rays which showed 6 cracked ribs & a cracked sternum.