This extremely large retouched metavolcanic flake is from near Hat Head on the north coast of New South Wales, in the traditional country of the Dunghutti People.  The flake is double-backed on the margin opposite from the sharp edge, and it was likely used as a chopping tool.  
The artefact is part of the Archaeology and Palaoanthropology teaching collection, University of New England.

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The blank for this tool was made by extremely hard-hammer percussion flaking of a water-rolled cobble of relatively coarse-grained metavolcanic stone.  One margin of the flake was then double-backed, with flakes initiated from both faces of the flake blank.  Most backed artefacts in the region measure less than 50 mm long, but this tool is nearly 200 mm long, making it an extreme outlier for backed tools in Australia.
Damage is present on the sharp edge (‘chord’) opposite the backed margin, suggesting that the tool was used for chopping.  It was likely hand-held and the backing was done to protect the hands.  Large-sized percussion flaking of water-rolled cobbles was widespread in the area around Hat Head; see this model for another example.