Hg porosimetry data for a carbon leader sample (E5-46-48-HS3I) and for a quartzite sample (from Western Deep Levels) indicate that the porosity of the carbon leader is approximately 1% and is greater than that of the surrounding quartzite. The permeability values calculated from the Hg porosimetry data by the approach of Swanson (1981) are below a microDarcy. The permeability of the carbon leader, however, is less than that of the quartzite. The reflects the pore size distribution which is smaller for the carbon leader than for the quartzite. The maximum pore size for the carbon leader is less than 0.1 microns in diameter. These measurements are consistent with SEM observations (Hoover pers. comm., 1999) which revealed that the carbon leader pores are filled with fine-grained mineral deposits. This indicates that intact bacterial cells must be residing within an extremely small volume fraction of the rock and are not likely to be migrating through the carbon leader. Bacterial migration is much more likely through the quartzite with the maximum pore throat size is 1 micron, but the low porosity would restrict bacteria to interconnected fractures. The data further indicate that it is unlikely that the internal nuggets of carbon leader microbial samples could have been easily contaminated by the bacteria borne in the mine's service water during drilling and blasting.

References:

Swanson, B.F. (1981) A simple correlation between permeabilities and mercury capillary pressures. Jour. Petrol. Technol.
    December: 2488-2504.