Using dd on Mac causes USB to become unreadable

I'm trying to create a bootable Arch Linux USB installer from Mac OSX El Capitan. I followed the tutorial on the Arch Linux Wiki, but when it "completes," I get a waing that The disk you inserted was not readable by this computer instead of getting a bootable USB media.

When finished, I get the following in $ diskutil list:

/dev/disk2 (exteal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *8.0 GB     disk2
   1:                       0xEF                         41.9 MB    disk2s2

The steps I followed to get this result were:

# insert USB flash drive

$ diskutil list      # yields /dev/disk2

$ diskutil unmountDisk /dev/disk2       # okay

$ sudo dd if=/Users/user/Downloads/archlinux-2016.08.01-dual.iso of=/dev/rdisk2 bs=1m

I enter my password, the thing runs for a few minutes, then I get the above listed error message. What have I missed? The tutorial lists no other steps or conditions required so I'm quite lost.

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