Phosphorus

Phosphorus was an element.

White phosphorus was used on matches in the late 19th century and could ignite from friction. (PROSE: The Death of Art) White phosphorus was also used in grenades and was colloquially known as "Willie Peter". (PROSE: Drift)

Phosphorus gave off a dull green glow. (PROSE: Divided Loyalties, The Scales of Injustice)