Specific Gravity Estimation with Minalyzer CS

June 2nd, 2016

Case Study

In exploration and mining it is important to know the density or specific gravity of rocks. Chemical analyses only report concentrations as a percentage of weight. In order to calculate the tonnage of an ore body, the commodity weight percent has to be multiplied by the rock density. After all, copper and iron are sold per ton!

A common but rather labour intensive method is hydrostatic weighing. The specific gravity is calculated according to Archimedes’s Principle by weighing the rock separately in air and water. The difference in measured weight is proportional to the buoyancy of the displaced water. Thus the specific gravity can be calculated relative to water (density ≈ 1 g/cm3).

Sensors in Minalyzer CS allow accurate estimation of the specific gravity of rocks, simultaneous with chemical analysis. This means that along with the XRF analytical results, there is an estimate of the specific gravity for each analysis. Calibration of the Specific Gravity curve is done by measuring samples with known specific gravity.


After applying the calibration curve, the relation between the hydrostatic specific gravity and Minalyzer CS specific gravity is a linear 1 : 1 ratio.sgcomp

Relative differences between the hydrostatic specific gravity and the estimated specific gravity by Minalyzer CS are generally less than ±10 %.