Cannot erase micro SD card
I was ready to follow the suggestions in the comments and put the SD Card in the .
However, Steve's comment brought up the idea that a camera might be able to format the card that the computer couldn't (even though the card's firmware lock was not a result of using it in a camera).
I tried putting the Micro SD in my Panasonic LX7 but got an error message right away (&quot;please reinsert the memory card&quot;). Then I placed the card in my Sony Nex 5 and the Sony was able to Format the card without a problem.

When I placed the card back into the Mac, it was repaired.
This solved my problem, but I am grateful for the comments that led me in the right direction.
I understand that a solution involving a mirrorless camera might not be accessible to everyone, but I would recommend to not trash SD cards that become locked after write errors, and to try formatting it in various devices that have a Format function.