A slurry density measurement system for measuring the density of a slurry within a region , the slurry comprising a mixture of solid and liquid components, the slurry density measurement system comprising: a plurality of electrodes arranged around the region; an energisation source arranged to apply an alternating electrical signal to at least one of said electrodes ; a monitor arranged to monitor an electrical parameter at at least one of said electrodes , the monitored electrical parameter being caused to change in response to flow of electrical current within the region; and a processor configured to: generate data indicative of the complex impedance of the slurry within the region based upon the monitored electrical parameter, wherein the data indicative of the complex impedance comprises data indicative of both real and imaginary components of the complex impedance; and generate data indicative of the slurry density based upon the data indicative of the complex impedance of the slurry, wherein generating the data indicative of the slurry density comprises generating data indicative of composition of the slurry, which further comprises generating data indicative of the modulus of the complex impedance of the slurry based upon the data indicative of both real and imaginary components of the complex impedance, and wherein generating data indicative of the slurry density is further based on a known conductivity of each component of the mixture and a density of each component of the mixture. a plurality of electrodes arranged around the region; an energisation source arranged to apply an alternating electrical signal to at least one of said electrodes ; a monitor arranged to monitor an electrical parameter at at least one of said electrodes , the monitored electrical parameter being caused to change in response to flow of electrical current within the region; and a processor configured to: generate data indicative of the complex impedance of the slurry within the region based upon the monitored electrical parameter, wherein the data indicative of the complex impedance comprises data indicative of both real and imaginary components of the complex impedance; and generate data indicative of the slurry density based upon the data indicative of the complex impedance of the slurry, wherein generating the data indicative of the slurry density comprises generating data indicative of composition of the slurry, which further comprises generating data indicative of the modulus of the complex impedance of the slurry based upon the data indicative of both real and imaginary components of the complex impedance, and wherein generating data indicative of the slurry density is further based on a known conductivity of each component of the mixture and a density of each component of the mixture. generate data indicative of the complex impedance of the slurry within the region based upon the monitored electrical parameter, wherein the data indicative of the complex impedance comprises data indicative of both real and imaginary components of the complex impedance; and generate data indicative of the slurry density based upon the data indicative of the complex impedance of the slurry, wherein generating the data indicative of the slurry density comprises generating data indicative of composition of the slurry, which further comprises generating data indicative of the modulus of the complex impedance of the slurry based upon the data indicative of both real and imaginary components of the complex impedance, and wherein generating data indicative of the slurry density is further based on a known conductivity of each component of the mixture and a density of each component of the mixture. <EOS>