Create Linux Mint USB on Mac OS/X

create-mint.sh

#! /usr/bin/env bash

# Insert a USB key.
# if needed initialize it with MS/DOS FAT and MBR

# Download the Mint ISO image
# Convert the ISO -> IMG
hdiutil convert -format UDRW -o linuxmint-18.3-mate-64bit linuxmint-18.3-mate-64bit.iso

# Run a diskutil list to know the device for the USB key, e.g.: /dev/disk3
# then unmount the USB key *** note the "r" ***
diskutil unmountDisk /dev/rdisk3    

# And copy the img on it:
sudo dd if=linuxmint-18.3-mate-64bit.dmg of=/dev/rdisk3 bs=1m

# Eject the USB key and voilà!