Sirillium

Sirillium is a volatile element found within some nebulae in its gaseous state.

In the 22nd century, Andorian and Tellarite vessels equipped their torpedo warheads with sirillium.

In 2381 during the invasion of the Borg Collective, USS Enterprise (NCC-1701-E) chief engineer Geordi La Forge detected sirillium on fragments of a Borg cube they destroyed at Korvat. Since it was only found on exterior hull pieces, they determined it had been picked up in transit. Only two sites near Federation space had sufficient concentrations - the Rolor and Azure Nebulae.