Before there was a mountain, there was molten rock.
The granite of this part of western Victoria formed around 350 million years ago, when magma cooled slowly two to five kilometres below the surface. That's more than 100 million years before the first dinosaurs.
For most of that time, the granite stayed buried. Over roughly the last 15 million years, erosion stripped away the rock above it and exposed the hard core we now see as Langi Ghiran's peaks. Weathering did the rest, breaking the granite into rounded tors and boulders, sandy gravels and clays.
Geologists use Langi Ghiran as the reference example for how groundwater moves through fractured granite across this part of western Victoria.

