Newmatter is a generalized name given to artificial elements, which have been created by mixing neutrons, protons, and electrons in subtly different variations. This process gives the resulting element different physical and chemical characteristics to anything that can occur in nature, as if they have been taken from a different universe.

The Forerunners made extensive use of newmatter, using machines (known to the Covenant as transmutators) that gave them incredibly-precise control over its creation. Millennia after the Halo event, the Covenant recovered several of these and use them to create highly-efficient metamaterials used in artificial gravity plating. Most of these were located on High Charity at the time that it fell, and were destroyed when the immense station crashed into the Ark.