Notable mining excavator manufacturers are Hitachi and Komatsu.
These giant diggers can reach over two million pounds!
Hitachi's giant is the EX8000-6 - weighing in at over 1.8M pounds. You can see Hitatchi's minging diggers here: http://www.hitachiconstruction.com/product-categories/mining-excavators-shovels/
Komatsu is also in the hall of giants. Their PC8000-6 is at 1.7M pounds. You can see Komatsu's models at: https://www.komatsuamerica.com/equipment/excavators/mining-excavators-shovels
The king of the diggers. Over two million pounds. The specs are online here: https://www.holtcat.com/Documents/PDFs/bucyrus/rh400.pdf