It is usually necessary to measure the density or specific gravity (SG) of drill cores and rocks, in order to be able to convert assay results from percent by weight to the actual mass. A great multitude of methods are traditionally used to estimate the density. For example by weighing a sample and dividing by the calculated or measured volume, alternatively by hydrostatic weighing in air and water to measure the SG. Less commonly used are gamma-ray densitometry tools available for drill core and downhole gamma-ray density logging tools. Density can even be measured on pulps using gas pycnometry.
X-SG is a method developed, tested and applied by Minalyze for estimating the SG value on a geological sample section based on the interaction between X-rays and the sample.
Apart from the characteristic X-rays are the incident X-rays that are scattered by the sample, known as Rayleigh and Compton scattering. The intensity of the scattered X-rays depends on the physical properties of the sample, including the density. This effect is for example used in healthcare applications to measure bone density.
Measuring density by Compton-scattered X-rays is with a long name called Compton-scattered X-ray densitometry, when applied and adapted to the geological field Minalyze simply call it X-SG.
X-SG works with a so-called backscatter setup, where the source and detector are on the same side of the sample. The photon energy and flux depend on the geometry of the setup, such as the scattering angle and beam energy.
The method is non-contact and deliver real time results. It is possible to get an SG estimation on any interval along the lenght that have been scanned with the Minalyzer CS. Saving time on the time-consuming task of SG measurements while also receiving a QA/QC able dataset.
The SG estimates are reliable and calibration of the Specific Gravity curve is done by measuring samples with known specific gravity. So far the method have proven to work exceptionally well on crystaline rock. Relative differences between the hydrostatic specific gravity and the estimated specific gravity by Minalyzer CS are generally less than ± 10%.
Specific Gravity Estimation with Minalyzer CSRead more