IT 5X Hydrous calcium magnesium silicate mineral mixture R. T. Vanderbilt Extenders / Fillers >> Calcium silicate Extenders / Fillers >> Talc or Magnesium Silicate Rubber - Elastomer (Chloroprene, Butyl …) Natural rubber (NR) SEALANT Used as fillers and extenders in specialized applications in NR and synthetic rubbers, sealants and mastics, especially latex compounds. IT ® 5X Hydrous calcium magnesium silicate mineral mixture For use in interior wall paints, exterior house paints, primers, maintenance paints and traffic paints. Used as filler and extender for coatings and elastomers. Hydrous calcium magnesium silicate mineral mixture. Used as filler and extender in NR and synthetic rubber, sealants and mastics.