- Open Terminal
- Enter the following: diskutil list
- Check which disknumber the USB-stick has. (disk0 or disk1 or disk2 etc)
- Enter the following: diskutil unmountDisk /dev/Disk# (Disk# = disk0 or disk 1 etc – see step 3)
- Open Disk Utility
- Click on the USB-stick
- Open the Erase-tab
- Choose the format you want (Mac OS Extended(macosx)/ FAT (windows))
- Click the Erase-button
- Once the erase is done, remove en replug the USB-stick into your Mac
