5. Phase seperation.
Temperature has an important influence on the equilibrium, so be careful not to heat the drop during examination. Sometimes crystals grow in the highly concentrated protein phase. Because of the unknown composition of the protein phase surrounding the crystal, mounting crystals can be a problem. Try freezing the crystal directly from the drop.
The protein is visible as small droplets within the drop. If the shape of the droplets is irregular it could be Spherulites. Check the drop with polarised light.