In mineral exploration it is important to realize early on whether further expensive digging will be successful or whether a mine will eventually be closed down.
One important analyzing technology beside the known mineralogical methods is spectroscopy. Depending on the analyzed minerals, reflection spectra are found in the near, shortwave, medium or even long wave infrared.
Because of the inhomogeneity of natural rocks it is important that a spectral analysis is not punctual but that large objects are analyzed with a spatially resolving method.
As this means large mines are analyzed over a large area, geologists and mineralogists prefer using imaging spectroscopy, a combination of wide area spectroscopy and digital imaging.
Our partner Specim is the leading manufacturer of hyperspectral imaging systems, a technology which offers spatially resolved spectral information. Contrary to conventional spectrograph-camera combinations, Specim’s spectral cameras provide full spectral information on each individual point. Thus, the distribution of an object’s spectral characteristics can be seen in one single image.
Spectral cameras consist of a spatially resolved spectrograph and a digital camera. The spectrograph’s entrance slit is small enough to provide information on only one line on the object.
The light is spectrally resolved in the spectrograph with both the spatial information and polarization maintained. It hits the detector inside the integrated camera that images the spatial position on the x-axis and the corresponding spectrum on the y-axis.
Each picture acquired provides information on the present spectral distribution on the line on the object. Up to 1600 spectra arranged in parallel with a resolution of up to 2 nm are possible. To get a two-dimensional spectral image of an object either the object or the spectral camera are moved. These spectral cameras easily allow line rates of 50 to 100 lines per second, making a two dimensional analysis of a large object possible within seconds. Figure 1 shows the relation between the material composition in a rock and its spectral response.
The graph was taken with a long wave infrared spectral camera. This information allows a qualitative and quantitative material analysis and mineral distribution evaluation.
Based on this information the usability of a mine in regards to the exploration costs can be estimated.
AngloGold Ashanti uses the SisuROCK hyperspectral core imaging at the La Colosa Prospect in Colombia.
They are one of the most known users of the Sisurock system and prove both the high feasibility of this technology and the enormous cost savings associated with it.
SisuROCK is a fully automated, hyperspectral imaging work station for easy, high-speed scanning of drill cores and other geological samples.
It is capable of imaging a single drill core in a high resolution mode or a whole core box in a high-speed scanning mode.
SisuROCK replaces the on-site visual inspection by a geologist with an objectified, automated system. The data is available in seconds, can be analyzed immediately and is easily stored for later evaluation without the need for keeping all drill cores in storage.
SisuROCK contains both an RGB camera to save images of the drill core and a VNIR and or SWIR spectral camera for spectral analysis in the relevant spectral ranges. The new SisuROCK systems can also be used with long wave infrared cameras. All in all, it provides a fast and comprehensive analysis of the exploration area including the corresponding documentation.
Other application fields are research groups using laboratory spectral cameras. SisuROCK is perfect for automated at-line measurements. It can be mounted on vehicles or tripods or even as a Specim AISA system on UAVs, helicopters or airplanes.