What is "vesbium"

Vesbium \Ves"bi*um\, n. [NL., from L. Vesuvius, contr. Vesbius, Vesuvius.] (Chem.) A rare metallic element of which little is known. It is said by Scacchi to have been extracted from a yellowish incrustation from the cracks of a Vesuvian lava erupted in 1631.

Note: It is not a recognized element. Actual identity?

n. (context chemistry obsolete English) A supposed rare metallic element extracted from Vesuvian lava, of uncertain composition.