Samsung Galaxy S3: Destroying my SD cards
I've been using my Samsung S3 for about two years now, with little issues with regards to microSD cards. However this week it started acting up. It started with my 64GB microSD card, which suddenly became "blank or unsupported" after I transferred some files from my phone to my MacBook via Kies. Tried formatting it on the phone—it doesn't work; just continually displays the same "blank or unsupported" message.
Replaced this microSD card with a second one; also 64GB. This one just unmounted suddenly while I was using it, and have not been able to remount it now.
Have tried both SD cards on USB SD readers, other Galaxy S3 units, on an S4 as well as an S5 (I have all three at home). Seems like the SD cards are gone for good. Any advice on this?