The attenuation capability of a hydrobiotite-vermiculite (HV) soil from southern Ontario is studied as a pollutant adsorbent landfill liner. The soil has specific surface areas varying from 90–206 m2/g, low cation exchange capacities (CEC) of about 10–20 meq/100 g of dry soil, a maximum dry unit weight of about 1.83 Mg/m3, and low hydraulic conductivities of 10-9 m/sec for the compacted samples. Increase in density with a corresponding decrease in hydraulic conductivity can be obtained by mixing the HV soil with kaolinite or Champlain Sea Clay. Heavy metal retention studies of HV soil and soil admixtures indicate that heavy metals retention can exceed the CEC of the soil, implying that other processes or mechanisms besides cation exchange such as precipitation are involved. While the HV soil alone shows satisfactory values for hydraulic conductivity (k= 10-9 m/sec), pH = 7–8, and high adsorption/retention of cations, especially heavy metals, the addition of Champlain sea clay in particular enhances or improves its performance.