How to download Raspberry Pi on an SD card from a Mac
Writing an SD card from OS X
You can figure out the name of your blank SD Card by first inserting the disk and running this command.
This will give you a path to the SD card. In my example (below)
2 means disk and
s1 means partition. Only focus on the disk.
Once you figure out the disk number of your card, unmount it.
Unmount the SD Card
sudo diskutil umount /path/to/your/dev/<Disk>
Copy over the DiskImage.img to the SD Card. Take note that we're now using
sudo dd bs=1m if=/path/to/your/disk/image.img of=/dev/rdisk<Disk Number>