Some mining stock bond ratings -
Newmont Mining - Baa2 (March 2020), Baa2 this is the 2nd lowest level within the 'investment grade' category, by Moody's.
Kinross Gold - Baa3, upgraded from Ba1 (March 2020), Baa3 is the lowest level within the 'investment grade' category
Yamana Gold - Baa3 (Aug 2019), revised up from negative to stable, Baa3 is the lowest level in the 'investment grade' category by Moody's
Hecla Mining - B3, upgraded from Caa1 (Jan 2020). These are not only junk bonds, but in the lower tiers of junk bonds.
Coeur Mining - Caa1, downgraded from B1 (May 2019), the C grades are the lowest levels of junk bonds, with only D being lower (bonds that are in default)
New Gold - B3, downgraded from B2 (Aug 2018), one grade above Caa1 within the junk scale