In your case (Apalis imx6 + Ixora board) SD car slot correspond to MMC device 1.
You can check status of SD card using commands:
Apalis iMX6 # mmc rescan
Apalis iMX6 # mmc dev 1
switch to partitions #0, OK
mmc1 is current device
Apalis iMX6 # mmc info
Device: FSL_SDHC
Manufacturer ID: 0
OEM: 0
Name: uSD
Tran Speed: 50000000
Rd Block Len: 512
SD version 3.0
High Capacity: Yes
Capacity: 7.4 GiB
Bus Width: 4-bit
Erase Group Size: 512 Bytes