Magnetic Resonance (MR) is a form of radio frequency (RF) spectroscopy that can be used for quantitative measurement of target ore minerals. In the MR technique, each mineral has a specific “resonance”, or response, at a particular radio frequency. The resonances are highly discriminating, as it is extremely rare for one resonance to overlap another mineral’s resonance. The method therefore involves tuning in to one or more specific minerals of value to the target operation.
Pulses of radio frequency fields are applied to the ore stream via non-contact sensors. The frequency of the field is set to a particular mineral’s resonance. A prompt radio frequency signature is then subsequently detected in the sensors in the form of an echo. This measurement process is normally completed in less than a millisecond.
Because of the discriminating nature of the mineral resonances, the magnitude of the echo is proportional to the number of crystalline unit cells of the target mineral.
Source: Bennett et al., Minerals Engineering (2009)
Key attributes
Deep sensing
Because RF fields penetrate tens of centimetres into most ores, the method can be applied to rocks, slurries or concentrate powders of large volumes, without the need for any sample preparation.
Highly selective
The presence of one mineral does not affect the capacity to sense another. The lack of overlapping mineral response frequencies mean that the MR method is very highly specific to the measurement of key minerals. There is no complicated spectral analysis or “background” stripping required; the magnitude of the MR echo is all that is used to estimate the mineral mass in the measurement zone.
No complicated calibration
Because the MR measurement is especially “clean”, there is no requirement for extensive calibration campaigns; often an accurate factory calibration can be pre-set.
Insensitive to surface conditions and moisture
As MR is a true bulk sensing technology, the measurement does not require presentation of clean surfaces, narrow size distributions, or premixed presentation to achieve a reliable measurement.
Fast, accurate measurement
The speed of bulk measurement outperforms all other technologies, such as nucleonic based techniques, leading to maximum achievable grade uplift in compact sorting applications. MR technology has been proven to result in sensing resolutions as precise as 0.047% copper in mining applications.
Target Minerals
| Chalcopyrite | Orpiment |
| Cubanite | Realgar |
| Covellite | Lollingite |
| Chalcocite | Niccolite |
| Enargite | Hematite |
| Tennantite | Magnetite |
| Cuprite+delafossites | Maghemite |
| Tenorite | Bismuthinite+others |
| Arsenopyrite | Stibnite+others |
Note: list is not exhaustive