After repeatedly erasing the new HD, the partition option allowed me to partition!! I'm not sure what happened except to say that the GUID scheme did become available after erasing the Lacie HD and then the untitled one underneath. It seems strange that I

had erased both before and I couldn't see the GUID option. However, Problem solved.

Thanks to those that responded.

jaybass


OS 13.6.6 iMac (Retina 5K, 27", 2017, 3.4 GHz Intel Core i5, 24 GB RAM, 2400 MHz DDR4. SuperDuper. 1 TB Lacie HD