An apparatus and method for determining the crystallization point of high pressure fluids comprising brine are disclosed. The apparatus comprises a temperature probe and an optical fiber probe to determine the temperature of formation and dissolution of crystals during cooling and warming cycles. The apparatus further comprises a pressurization source, preferably a positive displacement pump or connection to a positive displacement pump for pressurizing the sample. The apparatus further preferably includes a jacket for circulating coolant or heat transfer fluid to facilitate cooling of the sample. The method of the invention uses the apparatus of the invention to determine crystallization point of fluid samples.