You have a Lacie drive with lots of data in it but you are facing a problem where Lacie drive won't mount on Mac. You can not access any of your data of the drive, now you must first try to connect the drive with other system and then check. If the drive is mounted then the issue is with the Mac and if it is not mounted then you have to the drive has a problem. To fix lacie drive won't mount on mac you can reset the permission settings of the Mac and if the problem still exists then you can try to format the lacie drive which may have been corrupted and change its file system format to the hfs+ that is well compatible with the Mac. When you have fixed lacie drive won't mount on Mac then you will notice that all the content and the files have been erased. So you must now looking for recovering it. So you can use Lacie drive recovery software to get back your data, you have to choose the lacie drive for the scanning and then scan it. All the deleted files will be seen in the preview, restore them in Lacie drive now. You can download the marvelous software here.