Why can nigella oil sometimes be cloudy, flaky or even solid?
Some of the fatty acids solidify at low temperatures (e.g. when stored in the fridge) while most of the oil remains liquid. These fat crystal are visible as particles and can make the oil look cloudy. Since the oil is completely untreated, it contains fatty by-products which serve as crystallisation cores. This means that natural oils more easily become cloudy than refined oils.
The cloudiness is harmless and reverts again if you heat up the oil briefly (e.g. in a water bath or on your radiator).