late 2018 encrypted disk per https://openzfsonosx.org/wiki/Encryption
create new encrypted disk
plug in device
$ diskutil list
important to be absolutely certain of the device
$ sudo zpool create -f -o ashift=12 -O compression=lz4 -O casesensitivity=sensitive -O atime=off -O normalization=formD -O encryption=on -O keylocation=prompt -O keyformat=passphrase NAMEOFIT /dev/disk####
will interactively prompt for passphrase
next time importing plug in the device