A seller cannot convey what they do not own.
In my experience, property tax delinquency on minerals in Texas is not minerals at all. It is a working interest, overriding interest, or royalty interest (which are by definition in Texas, variations of mineral interest).
I would talk to a title attorney who specializes in minerals / royalties, or title company who produced the deed for Loving County that says they are intending to convey all mineral interest about this issue. If the county wrote up all deeds themselves, you may need to talk to the County Attorney or County Counselor.
When a property is delinquent, such as an individual royalty interest, and that interest is foreclosed and sold on the courthouse steps, it is only that interest - nothing more. Mineral interest is not taxed / assessed in Texas (Some could argue it is, but the value is $0). Variations of mineral interest, such as royalties, working interest, overriding interest, are taxed, and subject to foreclosure. In my county in Texas, they foreclose by individual property tax account. We tax a persons interest by each well they have interest in, even if they own interest in a unit or pool with multiple wells. So you can actually buy a portion of the same persons royalty interest, but only buy their interest in one well, and not the other wells in the same pool, since those are on different tax accounts. Irregardless, they are only auctioning off the royalty interest, and not mineral interest, since the mineral interest was not taxed. A sheriff's deed in this scenario I described should only convey the royalty interest, since the royalty interest was the only interest assessed and delinquent.
Please note that my statements here are limited to Texas only.