64gb SDXC Cards in Galaxy S2, or 64gb SDXC cards where only 32gb supported I spent hours looking for a solution to my issues with my 64gb Micro SDXC card that my girlfriend purchased me for my birthday.

From what I understand only capacities up to 32gb are officially supported. But thread after thread informed me that users of my phone had successfully used one. When I first plugged in my SD my phone said "Preparing SD card" and then, after a brief pause, "SD Card safe to remove". The card wasn't mounting.

I tried inserting it into my SD adapter and formatting in NTFS on my laptop. Side note - whoever designed SD adapters and ports can go straight to hell. I was terrified of damaging my expensive new card since it got stuck in the adapter, and the adapter left 1mm of space outside my laptop. Holy crap.

After formatting in NTFS the phone informed me it'd have to reformat the SD card. Progress, I thought, until after the formatting message I had the same issue.

I thought maybe my firmware was the issue and spent a couple hours trying to figure out how to jailbreak. Long story short I gave up.
The Solution: Thanks to the guys on This Thread I figured it out. I also used the same tool they described, Minitool Partition Wizard, though I'm sure you could use any partition tool.

In windows on an SDXC card you can only format in ExFAT and NTFS. With a third party tool, you can make the card a FAT partition. Once you do this, the card is recognized in my S2 with no issues. I assume this will work with other phones that have "grey" support for large capacity SDXC cards.

Hope this helped y'all!