Granite is a non porous stone with a dense crystal content. This enable the stone to stay hotter for longer periods during the treatment. Basalt is a porous product and this allows the stone to pick up and absorb dead skin cells that are exfoliated during each treatment. Without the dense content of crystals the Basalt stones fail to hold the heat as long as the Granite stones. The Basalt stones will pick up oil from regular use and stop heating efficiently unless they are cleaned or soaked in an epsom salt solution to draw out the oil. Basalt is still an enjoyable stone to work with but Granite is found to be a better and more practical option for everyday use in the Spa or Salon.