Gilsonite is a naturally occurring asphaltite, having specific gravity substantially equivalent to that of water.

Cross reference ice while it is of very light weight in comparison to most solids, it is not porous. Unlike perlite, which is presently employed as an aggregate for the lightening of oil and gas well cement, it does not absorb water, nor is it even wet by water. Thus, I have found that water requirements for making acceptable cement slurry, which may be easily placed as required and which will set firmly and permanently, are considerably less than those of perlite as an addition agent. I have found, moreover, that the strength of the set cement is greater than with perlite.
In the present composition, the Gilsonite serves as an aggregate which lightens the cement-water slurry, imparts valuable lubricating properties that reduce abrasiveness of the slurry, replaces a large portion of the cement ingredient and reduces shrinkage of the setting cement composition to an unusual extent, reduces compressibility of the set cement composition when in place, and insulates against undesirable loss or gain of heat by the well.