Billitonite is a rare regional variety of Australasian Tektite from Belitung Island, Indonesia, formerly known as Billiton Island. Locally known as ‘Batu Satam’, it forms part of the wider Australasian strewn field, produced by a major impact event around 790,000 years ago. Like other Tektites, Billitonite formed when terrestrial material was melted, ejected, rapidly cooled, and returned to Earth as natural glass. Its restricted occurrence on Belitung gives it a particularly focused geographic identity within the Australasian group.

Specimens of Billitonite are typically glossy black and often show deep natural pitting, grooves, and sculpted surface textures. Many pieces have a rounded or irregular form, with a bright enamel-like lustre that distinguishes them from more common Indochinites. Much of the material has historically been recovered during tin mining, where specimens were found in alluvial deposits. Their combination of dark glass, strong surface ornamentation, and localised origin gives Billitonites a very recognisable character.

For collectors, Billitonite offers a distinctive and less common branch of the Australasian Tektite family. Its Belitung provenance, characteristic glossy surface, and local cultural association as Batu Satam make it especially appealing for focused Tektite and impact glass collections. Each specimen represents natural impact glass shaped by a major cosmic event and preserved as one of Indonesia’s most recognisable Tektite materials.