Wow. I didn't realize it was that close to your house, thought it was out in a field somewhere.
I doubt it had anything to do with mining and probably more to do with the construction of the home. Poor backfilling, backfilling an extra large hole without compacting or burying organic materials like brush and stumps etc.
Do you have a basement there, often times when we find a sinkhole close to the foundation it means the silt/soil got washed down a footing drain system, or any perforated type storm water management system. Flowing with the path the storm water takes, yours is about twice as big as the biggest I've seen though, and it would usually show up causing storm water back up in basement.
Keep us informed. curious
JB.