An apparatus for the measurement of ore in mine haul vehicles, the apparatus comprising: a portal, defining a portal zone, wherein a haul vehicle carrying ore is positionable in or movable through the portal zone, at least one magnetic resonance sensor comprised in the portal, the magnetic resonance sensor comprising: a main loop positionable in the portal zone above or on an ore burden carried by the haul vehicle, a drive loop located above the main loop and electrically isolated from and magnetically coupled to the main loop, wherein a radio frequency transmitter is couplable to a feed terminal of the drive loop to drive an RF drive current in the drive loop and a radio frequency receiver is couplable to the drive loop to monitor an RF response current in the drive loop; the apparatus further comprising: a magnetic resonance sensor control system configured to control at least one of: positioning of the at least one MR sensor relative to the portal zone and/or ore burden; positioning of the main loop and the drive loop relative to each other; electromagnetic suppression characteristics of the at least one MR sensor; and/or sensitivity of the at least one MR sensor as a function of distance of the sensor from the ore burden. a portal, defining a portal zone, wherein a haul vehicle carrying ore is positionable in or movable through the portal zone, at least one magnetic resonance sensor comprised in the portal, the magnetic resonance sensor comprising: a main loop positionable in the portal zone above or on an ore burden carried by the haul vehicle, a drive loop located above the main loop and electrically isolated from and magnetically coupled to the main loop, wherein a radio frequency transmitter is couplable to a feed terminal of the drive loop to drive an RF drive current in the drive loop and a radio frequency receiver is couplable to the drive loop to monitor an RF response current in the drive loop; a main loop positionable in the portal zone above or on an ore burden carried by the haul vehicle, a drive loop located above the main loop and electrically isolated from and magnetically coupled to the main loop, wherein a radio frequency transmitter is couplable to a feed terminal of the drive loop to drive an RF drive current in the drive loop and a radio frequency receiver is couplable to the drive loop to monitor an RF response current in the drive loop; the apparatus further comprising: a magnetic resonance sensor control system configured to control at least one of: positioning of the at least one MR sensor relative to the portal zone and/or ore burden; positioning of the main loop and the drive loop relative to each other; electromagnetic suppression characteristics of the at least one MR sensor; and/or sensitivity of the at least one MR sensor as a function of distance of the sensor from the ore burden. positioning of the at least one MR sensor relative to the portal zone and/or ore burden; positioning of the main loop and the drive loop relative to each other; electromagnetic suppression characteristics of the at least one MR sensor; and/or sensitivity of the at least one MR sensor as a function of distance of the sensor from the ore burden.