Obsidian in Australia: Why It's Not Naturally Occurring

Geological Absence

There is no naturally occurring obsidian in Australia.

Why?

• Tectonic setting: Australia sits on the stable Indo-Australian Plate, far from active subduction zones or mid-ocean ridges where rhyolitic volcanism produces obsidian.
• Volcanic history: Most recent volcanism (e.g., Victorian Volcanic Plain, ~5,000 years ago) was basaltic—low silica, high iron—forming scoria, not obsidian.
• Age & erosion: Ancient felsic provinces (e.g., Gawler Craton) are deeply eroded; any volcanic glass has devitrified to crystalline rock over billions of years.

Archaeological Context

• Aboriginal Australians did not have local obsidian. Trade networks moved stone (e.g., Kimberley points, greenstone), but obsidian artifacts found in Australia are imported (e.g., from Papua New Guinea, Indonesia, or post-contact).
• Nearest natural sources: New Zealand (Mayor Island), Papua New Guinea (New Britain), Indonesia (Java, Sumatra).

For knappers or researchers in Australia, obsidian must be sourced internationally.