Sheep scrapie and cervid chronic wasting disease (CWD) are unique among transmissible spongiform encephalopathies (TSEs), or prion diseases, because they are horizontally transmitted.  The misfolded isoform of the prion protein (PrP^Sc), the likely etiological agent of TSEs, is resistant to inactivation, and TSE infectivity persists when buried for at least three years. PrP^Sc is thought to be shed into the environment from scrapie- and CWD-infected animals. The agent also likely enters the soil when carcasses of infected animals decompose. Healthy sheep or deer have become TSE infected after occupying land or paddocks previously containing diseased animals or carcasses, suggesting environmental transmission of disease. We examined the potential for soil to serve as a TSE reservoir by studying the association of PrP^Sc with common soil minerals. We demonstrate substantial PrP^Sc adsorption to two clay minerals and lesser sorption to quartz surfaces. The interaction between PrP^Sc and montmorillonite (Mte) clay was strong, making desorption of PrP^Sc from Mte surfaces difficult. Several extractants, including strong chaotropic agents like guanidine or urea (8 M each), failed to remove PrP^Sc from Mte surfaces.  Of the tested compounds only sodium dodecyl sulphate effectively extracted the PrP^Sc. PrP^Sc desorbed from Mte was cleaved at an N-terminal site. Despite the remarkably avid adsorption to Mte, sorbed PrP^Sc remained infectious. Our results suggest that soil, and particularly clay minerals, could contribute to the environmental transmission of scrapie and CWD.