Can't format samsung 128 evo micro sd card I'm having issues formatting a micro sd card a for a friend on my Mac. I've tried using Disk Utility, diskutil commands in terminal and SD Card Formatter. This is what I get when I try on terminal:

jonathandiller$ diskutil unmountDisk /dev/disk2
Unmount of all volumes on disk2 was successful
jonathandiller$ sudo diskutil eraseDisk FAT32 NONAME MBRFormat /dev/disk2
Started erase on disk2
Unmounting disk
Creating the partition map
Waiting for partitions to activate
Formatting disk2s1 as MS-DOS (FAT32) with name NONAME
Error: -69830: This operation requires an unmounted disk
In the half-dozen or so instances where I've seen this specific error, the micro SD card itself had gone bad and couldn't be formatted on Mac, Windows or Android (via OTG), even with different card readers. Not only couldn't the card be formatted, but files couldn't be added or deleted nor anything else that required writing to the card. (Reading files was unaffected.) It was effectively in read-only mode like a full-size SD card with the switch flipped, but obviously the micro SD doesn't have that. Only solution is replacement.

I know this is an old post, but I thought I'd add the real cause (i.e. a defective card, not a software or format issue)  for future reference.