Gilsonite "Natural asphalt ,Natural Betumen" together with a continue layer or in three ply with two layer of a water proof and permanently natural asphalt cement.
It is surface coated after it is laid on the roof with very durable liquid asphalt. The best advantage is saturating and cementing together with felt and surface. Application of the material and petroleum seepages goes back to ancient times, when people in southwest of most countries used these for fuel and medication purpose. In ancient Egypt these material were also used in mummifications. It is a product of crude oil and forms as it migrates toward the ground surface, this material is using as industrial material now.