In The Bloody Sun. Chapter 9, the matrix workers at Ariliin agree to do a geological survey using their powers, to forestall a survey that otherwise would be done by the Terrans. They are to search for "tin, copper, silver, iron, tungsten" and for "fuels, for sulfur, hydrocarbons, chemicals[.]" The purpose is to prevent Terrans and their "infernal machines" from spreading across Darkover. They succeed in locating mineral deposits and marking them on maps (ironically, maps created using the assistance of Terran surveys), but the effort, at first successful, is abandoned.