Debian..Can't format and mount external HDD

I have been trying to format my 640GB external Hard Drive in command-line and can't seem to get it working.

I have done the following in order:

sudo fdisk /dev/sda

(Deleted any partitions, created a new partition, toggled partition type (tried multiple, but not sure the best?), then wrote the partition and printed to make sure it was correct.

I then created the ext4 filesystem using: sudo mkfs.ext4 /dev/sda1

I tried to mount the partition using: sudo mount -t ext4 /dev/sda1 /mnt/640-hdd -o gid=XXXX,uid=XXXX

I then was given a mount error:

mount: wrong fs type, bad option, bad superblock on /dev/sda1,
    missing codepage or helper program, or other error
    In some cases useful info is found in syslog - try
    dmesg | tail  or so

Any recommendations?