Jojoba oil freezes when the temperature goes below 7⁰C, and thaws when the temperature rises. You can just let it come to room temperature to use it, as it should go back to liquid with no damage done to it. It's a highly stable carrier oil - think of it as a a liquid wax with two double bonds and one ester group in each molecule that actually goes into a wax-like state when it's chilled. As the ingredients and formulation are not heater, then it should still be usable and mixable, as it's properties wont change just because of low temperature!