Is it possible to find the salt for a known password?

I have a hash of the form of 64 hex chars (I'm assuming SHA256???)

Im told that it has some form of salt prepended to the string before hashing, and I have the unhashed string, but not the salt.

Is it possible to find the salt?

I have tried:

hashcat -m 1400 -a 1 ./hashfile /usr/share/dict/american-english ./known

(Combination attack mode), where "known" contains the known string. But it only seems to load one dictionary. And of course I don't know that the salt is a dictionary word.

Any advice appreciated - I'm knew to this sort of thing in general, and hashcat specifically!

Thanks!