I bought a new jar of tahineh (aka "sesame butter")at our local Asian grocery today. It must have been in stock for a bit because the oil had separated and risen, and the butter part was VERY stiff. I tried mixing it but boy it was hard. Would it help to heat it, in order to blend it back together? :-\ Please help!
Whenever I worked at a ma and pa deli we made our own hummus from scratch using tahini and we used to store the tahini in the fridge for months and it lasted. It's naturally thick. But in your case it sounds a little too thick. If I were you I would return it with the receipt. I suppose you could try heating it; I doubt it would ruin the general product. Perhaps store in the fridge upside down and try mixing it afterwards. If that doesn't work, try adding a little sesame oil to mix it up. I'm curious to see what happens, so post your results. I hope this helps :-\
My sister used to work in the bulk section of a health food store and she would have to stir up all the nut butters. What she found out was that it was so much easier to stir when they were at room temperature. If you try leaving the tahini out at room temperature for a few hours, and then mixing, I think it would work.