Can't format a Micro SD card?

Could it be something very simple?

On the SD Card Adapter there is a little sliding "Tab" on the left side:

Slide the Tab UP, and the card is unlocked "Read/Write", slide the Tab DOWN and it is locked and "Read Only"...

Might the Tab on the SD Card Adapter have moved to the lock position?

Double check that, and see if it toggles to unlocked for Read/Write Ability...

I'm not familiar with Android. Can you reformat on the tablet? I would also try to see if I had another device that might be able to read/reformat the card. For example a camera or a Windows computer if you have access to that. A final thought would be to try a disk utility alternative such as Paragon Hard Disk Manager for Mac (https://www.paragon-software.com/home/hdm-mac/) -- I believe it has a trial period.

Hope that helps.

My answer is to keep trying. Choose a different partition map, such as GUID Partition Map. Try erasing the partition first using Mac OS X Extended or some other format. It – should – work. Some cards don't respond fast enough for Disk Utility.

Be sure the write protect switch isn't becoming inadvertently closed while inserting the SD card. That's easily overlooked, especially with a card adapter that doesn't have a positive detent.

southwestform wrote:

The card will be used in an Android tablet

Formatting GUID will not work on your Android.

Try formatting in a camera or other PC device

http://www.howtogeek.com/235596/whats-the-difference-between-fat32-exfat-and-ntf s/

John Galt wrote:

My answer is to keep trying. Choose a different partition map, such as GUID Partition Map.

To clarify the above, you might need to choose a different partition map only as an interim step, before formatting it for whatever Android needs. The idea is to choose something different than you have been trying.