Ground Level

The quarry floor at Hornsby Quarry sits roughly 120 metres below the southern rock face, a flat expanse of exposed ground ringed by near-vertical walls of dolerite and volcanic breccia. Concrete foundations remain where processing equipment once stood, their bolt patterns and pad footings still legible against the open floor. Nothing else is left at ground level. The walls do the talking. What those walls expose is a cross-section through a Jurassic diatreme, a volcanic neck between 146 and 200 million years old, the largest of its kind remaining in the Sydney area. Quarrying here began around 1905, when the Higgins family started extracting dolerite from the site they had farmed since the 1830s. Hornsby Shire Council recognised the strategic value of the material early and purchased the operation in 1912 to secure a reliable supply of blue metal for road construction across the northern suburbs. Ownership passed to Hornsby Blue Metal Limited in 1924, then to a Farley and Lewers subsidiary in 1959, then to CSR Construction Materials following CSR Limited's acquisition of Farley and Lewers in 1980. At its projected rate of around 110,000 tonnes per year, the quarry was expected to keep producing well into the 2020s. Instead, extraction ceased in 2002, and Hornsby Shire Council acquired the site in 2003 for $26,508,771.28, the amount determined by the NSW Land and Environment Court. This photograph was made in 2015, more than a decade after the last load of blue metal left the site. The foundations sit in the open. The walls that were blasted back and back again across the twentieth century now stand static, their layering intact. A 2022 geoheritage assessment by geologist Ian Percival classified the exposed face as an internationally significant reference site. The ground beneath it built the roads above it. Part of the Hornsby Quarry series.