iMac 2012 won't read 64 g micro SD card

[Racineur]

Hi, my late 2012 iMac 27 won't recognize, mount and read a 64 g micro SD card that I use in a Samsung Galaxy Tab 3. Tried different card readers but with no success. What is the workaround if there's one to get the iMac to mount the card? Or who's the culprit? My card readers? The card itself? The iMac itself? The card is a Kingston class 10 - HC. Would appreciate a lot infos and cues on this one.
Thanks. R.

 

[Intell]

Does the card show up in Disk Utility?

 

[Racineur]

Does the card show up in Disk Utility?

No. DU shows only ext traditional HD and Fusion Drive. The card is non existant.