Isocryte was a mineral which was formed during extreme conditions of atomic stress, such as collision of stars. It was usually found in galactic cores or at the centre of star clusters. The mineral was not chemically unusual, but had a unique subatomic structure. According to the Second Doctor, electrical and mechanical stimulation of isocryte such that its energy fields interacted generated counter-gravitic waves.
It was found in unnaturally large amounts on Vortis. This was due to its use by the Gods of Light in their experiment there. Isocryte counter-gravitic properties, meant its consumption by the Menoptera allowed them to fly, which they would have otherwise been unable to do by the power of their wings alone. (PROSE: Twilight of the Gods [+]Loading...["Twilight of the Gods (MA novel)"])