Southeast Michigan. I contacted the company with the shale and they said shale is shallower than petroleum and a different beast, can't be ignited is safe for humans, pets etc.
Searching for a company that does natural lawn care in my area. A company says they feed with products derived from "humic shale" which they describe as 75 million year-old decomposed matter drawn from the earth. Isn't this the definition of Fossil Fuel/petroleum?