Although they are generally referred to as massive sulphides, strictly speaking the deposits at hydrothermal vents are characterized by 3 different kinds of sulphur associations: sulphides, sulphates, and native sulphur. Which compounds predominate depends on the temperature of the hydrothermal vent as well as the chemical conditions in the hydrothermal fluid. The hottest known vent has a temperature of 407 degrees Celsius. At all others the temperature of the escaping liquid is significantly lower. Sulphides predominate at hydrothermal vents with temperatures between 330 and 380 degrees Celsius. Because these sulphur compounds are black, the vents are called black smokers. At white smokers, on the other hand, the prevailing temperatures are below 300 degrees Celsius. White sulphate compounds are more abundant here. There are also grey smokers that discharge both sulphides and sulphates. Yellow smokers occur in some regions. These are located at active volcanoes. The water temperatures here are below 150 degrees Celsius and primarily yellow native sulphur is extruded.