The factors used to convert metal assays to mineral assays in this MVT Mississippi Valley Type Deposits review is summarized below. The conversion factors are based on standard metal to mineral gravimetric factors with some minor adjustments to compensate for the interstitial iron contained in the sphalerite lattice.
The measured value for interstitial or submicroscopic iron in the sphalerite were estimated using differential point count methods for each set of sized mounts. The results of these estimates are displayed below. Microprobe analyses to actually measure the range of solid solution iron values in the sphalerite lattice are recommended.