Okay, so we've excluded a "fake" card.

Oops, sorry. As you're playing around with a slightly beta OS, and using parted I kind of assumed you were fluent in linux.
Sorry, my bad !

The thing that interests me is something like :

/dev/mmcblk1p1 on /media/sdcard/<some long hexdecimal string> type ext4


(an easy way would be to pipe, to connect to another command like grep that can filter : "mount | grep mmc")

That would be a sign that at least the system is trying to mount it.

In linux, devices on the SD/MMC bus tend to show as /dev/mmcblk<n>
where n is the device.
On sailfish device, mmcblk0 is the embed flash "eMMC" that contains the system (the 32 GB of the Xperia X), and mmcblk1 is the microSDHC / microSDXC card.
mmcblk1p1 is the device as which the first partition (p1) shows up.

For some weird reason, the service in charge of automatically starting the mount didn't start.
(On Sailfish X, sd-mount is the service in charge of mounting stuff plugged in)

("systemctl | grep mmc" can help to filter)

First something, extremely useful : in bash (the shell on which you're typing commands) "tab" key auto-completes. (or if there are more choice, advances to the point where there are more choices, and the next tab displays you a list of possible commands). That's really useful, because paths like "/dev/mmcblk1p1" would otherwise be easy to mistype.

"devel-su" : sailfish x specific way to as root. It will ask your password (again), and the the prompt will change from 'nemo' (the default user) to 'root' (the admin).

then :
"mount /dev/mmcblk1p1 /mnt/sdcard/"

check for any error message.
check also the system log : still as root, "journalctl --since '5 min ago' "

other useful stuff (all need root, because all need direct access to the blocks on the device) :

"blkid /dev/mmcblk1"
gives info about what it detects on the raw card (should detect your partition table)

"blkid /dev/mmcblk1p1"
tries to detect the 1st partition

"lsblk" (list all the known block device) or "lsblk /dev/mmcblk1" (only the partitions on your card).

"fdisk -l /dev/mmcblk1p1".

Whenever a command displays an error message instead of what you would expect, remember to peak in journalctl (still as root)



journalctl and systemctl use a list display mode similar to "less" when they have a giant list that goes beyond the content of your screen.
You can scroll and pageup/down, and the "/" key brings a search box.
you can type "/mmc"+enter to search for the first occurence of the string, then "n" or "N" to go to next / and previous match.

another possibility is to open a second putty session and have
again as root ("devel-su") "journalctl --follow" running an constantly display new log message as they come by.