It's probably pretty well separated. Mix it up real good and try some. If your sample cures right and acts OK, it's good.
If it doesn't, get some fresh hardener and try it again.
I worked at US Perogygen in Richmond, CA for a few months in 1964 between Air Force and College. I ran the machine that mixed most of the body filler hardener for the entire country.
The only variation between brands was the color pigment I dumped in the 2 or 3 cubic yard mixing machine. I remember 50 lbs or more of pigment in some of the batches. After about a month on the job I broke out in ahead to toe rash and got transfered to another operation.
Lovely place to work. I really pine for the good ol' days before the gumnt started interfering with all those wonderful businesses.