To locate the disks, In this case locating the SD card

use `diskutil list`


```sh
$ diskutil list

/dev/disk0
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *500.3 GB   disk0
1:                        EFI EFI                     209.7 MB   disk0s1
2:                  Apple_HFS Macintosh HD            399.5 GB   disk0s2
3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk1
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:     FDisk_partition_scheme                        *15.9 GB    disk1
1:             Windows_FAT_32 NO NAME                 15.9 GB    disk1s1  <<< this is the sd card
```

to erase use following command by adding your desire name and drive address

`sudo diskutil eraseDisk Fat32 <Name> MBRformat <drive address>`

For example

`sudo diskutil eraseDisk Fat32 RPI3 MBRformat /dev/disk1`