Borax Is The Common Name For Sodium Tetraborate: A Naturally Occurring. Substance Produced By The Repeated Evaporation of Seasonal Lakes. 20 Mule Team Borax Is 100% Natural; And 99.5% Pure (there Is About A Half of 1% of Naturally Occurring Trace Minerals). Once Removed From The Ground It Is Washed; Dried; And Boxed For Consumers.