mounting local file

[Verde Denim]

I have a local file on my Ubu box that I made using dd from an SD Card.
For whatever reason,
mount -o loop <file-name> /mnt asks for the filesystem type, and regardless
of the type I supply, mount tells me that it doesn't recognize the type.
file <filename> tells me that this is an x86 boot sector with an extended
partition table, but does not reveal the filesystem type.
am I hosed for being able to mount this file?

any input, as always, is greatly appreciated.
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