Freezing Olive Oil | The Olive Oil Source
"Oil that has not been winterized will clump and form needle-like crystals at refrigerator temperatures as the longer chain fats and waxes in the oil congeal, but the oil will not usually harden completely unless chilled further. Some olive varieties form waxes that produce long thin crystals, others form waxes that congeal into rosettes, slimy clumps, clouds, a swirl of egg white like material, or white sediment that the consumer may fear represents spoilage. These visual imperfections also may form outside the refrigerator during the winter when oil is exposed to cold temperatures during transport. The white color in the hardened oil does not indicate spoilage."
I thought this was interesting information--above.
I'm not aware of any visual clues to an oil being rancid. I thought the only way to tell if oil was rancid was by taste and smell. HTH