Landlord said I could paint the fireplace mantel & surround. So, I did. White for mantel & faux painted a 'marble' on the tile. A lot of work, but I had to look at it every day, & it was disturbing my 'wa'. Landlord is pleased.

Don't know what the deal was with the swirly stuff on the hearth around the tile, but I didn't want to mess with it (I mean, I could have fixed it, but it's a rental, so . . .), so just painted it.
BTW, always happy to dispense advice if you need help with a project.