WIMP detection requires exposure
times of 
kg-years. A novel approach
is to replace the
100 kg detector with small amounts of material that
has been exposed for nearly a billion years.
Snowden-Ifft and collaborators [62] have looked
for tracks produced by WIMP scatters off of
heavy nuclei (such as cadmium) in ancient Mica.
They identify these tracks by etching the Mica
and have calibrated their experiment by
bombarding the Mica with a neutron source.