The In-Situ CHEmical MINIaturized analyzer (CHEMINI) is an instrument developed by IFREMER that measures dissolved chemical parameters in seawater including iron, nutrient salts and sulphur. CHEMINI is one of the sensors on Tempo-Mini, installed at Endeavour Ridge, and used to measure iron (Fe) properties near hydrothermal vents.

The study of chemical parameters at hydrothermal vents is important. As hot effluent encounters the cold seawater (~2 degrees C), minerals precipitate from the element-rich vent water. Black smoker vents are found in areas where the effluent is very hot (~350 C). These types of vents precipitate iron sulphides, giving rising plumes a dark colour and cause the formation of sulphide-mineral deposits on the seafloor.