Natural peanut butter may be delicious, but it does have the annoying habit of separating out. Storing it upside down can help, but if you find yourself confronted with an oily, un-spreadable jar of nut butter, use your hand mixer to smooth it out.
Photo by Matias Garabedian.
The link below has a video that can show you how it's done, but all you need to do is remove one of the beaters from your mixer, stick the remaining beater in the jar and -- keeping a very firm grip on the jar -- mix it using medium speed. Remove the beater, and spread your now homogeneous peanut butter (or almond butter) with ease.
The Amazing Trick for Mixing Natural Peanut Butter [Tasting Table]