MicroSD now not readable?

Hi All,

I had been successfully running my iTunes from a Kingston 128GB microSD XC I class 10 card, inserted into my macbook air using the Nifty MiniDrive.

The mac seemed to freeze up so (against common advice) I forced a shut down. Since then, I get the following message appear and cannot use the microSD:

'The disk you inserted was not readable by this computer' and gives me 3 options - Initialize, Ignore or Eject.

In Initialize, verifying the disk prompts me to repair it, but it says it cannot be repaired. It suggests that I back up the files and reformat, but how can I backup when it doesn't read? I have also read somewhere that I can click 'erase' but this seems to me like I will lose everything on the disk (if not already lost) so I'm reluctant to go this route unless someone tells me otherwise.

Other details I have form the card:

Mount point - Not mounted

Format - ExFat

Details I have from the mac:

OS X Yosemite 10.10.2 (I updated to this software after the initial problem occurred, thinking that it may help aid a solution)

Best case scenario for me would be to get my iTunes library back, as the last back up was a while ago and I have done a lot of tidying up since then. Nifty have offered to replace the card but won't deal with recovering the content on it.

Lessons learnt so far - back up, back up, back up. Don't trust that new ideas and new products won't cause you problems!

Thanks in advance for anyone taking time to help me out here,

Joe