Windows – Create HFS+ Partition on Existing NTFS Drive

Other free utilities you can try are:

DiskDigger

DiskDigger can recover files from any type of media that your computer can read. This includes USB flash drives, memory cards (SD, CompactFlash, Memory Stick, etc), and of course your hard drive. The types of files that it recovers include photos, videos, music, documents, and many other formats.

DiskDigger can even scan reformatted or badly formatted disks (disks to which Windows can’t assign a drive letter), and even disks with bad sectors. It bypasses the Windows file system drivers and scans your disk directly. It has its own built-in support for the following file systems: FAT12 (floppy disks), FAT16 (older memory cards), FAT32 (newer memory cards and hard disks), NTFS (newer hard disks), and exFAT (Microsoft’s new successor to FAT32).

PC INSPECTOR File Recovery 4

PC INSPECTOR™ File Recovery 4.x is a data recovery program that supports the FAT 12/16/32 and NTFS file systems.
Here are some of the new features in PC INSPECTOR™ File Recovery 4.x
- Finds partitions automatically, even if the boot sector or FAT has been erased or damaged
- Recovers files with the original time and date stamp
- Supports the saving of recovered files on network drives
- Recovers files, even when a header entry is no longer available. Competition products cannot recover such files. The "Special Recovery Function" supports the following disk formats: ARJ AVI BMP CDR DOC DXF DBF XLS EXE GIF HLP HTML HTM JPG LZH MID

I tried various other search terms and found that this question is actually a duplicate of this one: OS X 10.6 Snow Leopard no longer mounting an external USB drive.

Here's what I did to fix:

1. Download and install GPT fdisk

2. Run gdisk and select problem drive:

   ~% sudo gdisk
   GPT fdisk (gdisk) version 0.8.1
   
   Type device filename, or press <Enter> to exit: /dev/disk3
   Partition table scan:
     MBR: protective
     BSD: not present
     APM: not present
     GPT: present
   
   Found valid GPT with protective MBR; using GPT.
   

3. Look at the partitions using the p command:

   Command (? for help): p
   Disk /dev/disk3: 1953525168 sectors, 931.5 GiB
   Logical sector size: 512 bytes
   Disk identifier (GUID): ABFA9105-73F4-4627-9890-9DECC55E86AC
   Partition table holds up to 128 entries
   First usable sector is 34, last usable sector is 1953525134
   Partitions will be aligned on 8-sector boundaries
   Total free space is 3389 sectors (1.7 MiB)
   
   Number  Start (sector)    End (sector)  Size       Code  Name
      1              40          409639   200.0 MiB   EF00  EFI System Partition
      2          409640      1367597143   651.9 GiB   0700  Time Machine Backups
      3      1367599104      1953523711   279.4 GiB   0700  Basic data partition
   

   In this case, it's partition 2 that's causing the problem. And the problem is that its type code is 0700, which means something other than HFS.

4. Use the t command to set the partition type to af00 - Apple HFS/HFS+.

   Command (? for help): t
   Partition number (1-3): 2
   Current type is 'Microsoft basic data'
   Hex code or GUID (L to show codes, Enter = af00): 
   Changed type of partition to 'Apple HFS/HFS+'
   

5. Use the w command to write the stuff back to disk and quit.

   Command (? for help): w
   
   Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
   PARTITIONS!!
   
   Do you want to proceed? (Y/N): y
   OK; writing new GUID partition table (GPT).
   Warning: The kernel may continue to use old or deleted partitions.
   You should reboot or remove the drive.
   The operation has completed successfully.
   

The HFS+ partition, and all of its contents, then became visible again to OS X.