Abstract: The invention relates to a thermally stable composition, and methods for the preparation thereof, for use in the manufacture of a lightweight aggregate including a continuous bituminous phase, a discontinuous aqueous phase, an anionic oxide suspended in the discontinuous aqueous phase and at least one emulsifying agent. The anionic oxide may be a naturally occurring metal oxide having a needle-like crystal structure such as red oxide (CuO) or yellow oxide. The continuous bituminous phase may be for example grade 170 bitumen or crude oil, hydrocarbons or mixtures thereof. The emulsifying agent may be a clay emulsifier such as sodium bentonite, or a hydrous aluminium silicose or montmorillonite clay. The invention also relates to lightweight aggregate particles coated with such compositions and building materials formed from the lightweight aggregate in combination with a cementitious material.