fuller's earth
From Longman Dictionary of Contemporary Englishfuller's earthful‧ler’s earth /ˌfʊləz ˈɜːθ $ -ərz ˈɜːrθ/ noun [uncountable] DCBdried clay made into a powder that is used to clean cloth or oilExamples from the Corpusfuller's earth• The occurrence of fuller's earth in Cretaceous strata from Wiltshire to Yorkshire has been studied.