Half my storage missing after fusion drive partitioning
I have a late 2015 5K iMac with a 3TB fusion drive running High Sierra 10.13.6. Until now i was using it as one big HD but yesterday decided to partition it into two equal halves using Dick Utility, so that I could install MojaveOS onto the second partition. Everything was running smoothly, it took around 4-5 hours to complete the process. I kept checking back and watching the progress ( I have 1.2TB of data in the disk ). The last time i checked the computer had rebooted and i needed to log in, so I did and now my HD is half the size (as expected) but the new partition is not showing up. Its not on the desktop and Disk Utility isn't showing it either! HELP! What could have gone wrong and how to fix it?
More info: Disk Utility is showing the internal storage (Called Fusion Drive) as a 'CoreStorage Logical Volume Group' with a capacity of 3.12TB and revealing the contents with the reveal triangle shows only one icon called Macintosh HD which is a 'CoreStorage Logical Volume' with a capacity of 1.56TB.
Any help very gratefully received. Thanks in advance.