Pyrmont is one of Sydney's most densely populated suburbs, its sandstone cliffs studded with apartment towers and luxury units angling for a glimpse of the shimmering harbour.
But nestled behind the Star Casino, on a development site in Harris Street, is an excavation project which provides a glimpse into Sydney's colonial past.
Over the past six months, machines have buried metres into the earth, clearing away the upper sandstone crust to access the "yellow gold" beneath.
It is not precious metal they are harvesting, but the coveted yellow block sandstone used to build many of the city's great public buildings during the mid-19th and early 20th century.
The State Library of NSW, the Australian Museum, the GPO building, the QVB building, just to name a few, were all hewn from Pyrmont's yellow block sandstone.
Troy Stratti, managing director of Bundanoon Sandstone, the company excavating the Harris Street site, said the value of yellow block was in its link to the past. There is little commercial demand for it otherwise.
"It is sought after in the sense that it is a stone needed now for heritage restoration," he said. "It's important not to look at it in commercial way. There's a social responsibility here."
Human-sized saws have already sliced and diced some 2000 cubic metres of sandstone into geometrically-precise blocks.
Mr Stratti is hopefully the total yield will be double this, and some 1300 blocks will be extracted before the project wraps up early next year. At that point, developers TWT developments will begin building high-end terraces on the site.
Most of the stone, he said, will be used to replenish the government's dwindling yellow block supply at the government-run Ministers Stonework Program, where it will be used by stonemasons to restore the city's heritage sandstone buildings.
It will likely be used in restorations works for Sydney's Town Hall, the University of Sydney and the Queen Victoria Building.
The Harris Street quarry could boost the government's yellow block supply by another 10 years, Mr Stratti said. Future projects, however, would boil down to a race for access to sites before they are entombed by development.
"The important story here is the government needs to move quickly when these opportunities come up, and they need to look at what their part in making it happen needs to be," he said.
More than century and a half ago, the Pyrmont peninsula, spanning the colonial streets of Ultimo to the headland, was pock-marked with quarries harvesting sandstone for the city's public buildings boom.
From the mid-1800s until the early 20th century, quarrymaster Charles Saunders and his son ran the three most famous sandstone quarries in the area. They were named Paradise, Purgatory and Hell Hole by the stonemasons, a reference to the quality of the stone and the difficulty involved in extracting it.
The best "paradise" stone was yellow block. It was prized for its strength and easy manipulation. When freshly harvested the stone is soft and grey, but it hardens as it oxidises and changes to a rich honey colour over a number of weeks.
Mr Stratti is confident more yellow block is buried beneath the Fish Market carpark and the derelict Rozelle Rail Yards – both of which have been slated for redevelopment.
He has already discussed the Fish Market site with government representatives, framing it as the government's social responsibility to consider the harvesting potential before development occurs, he said.
The story Pyrmont quarries provide portal into Sydney's colonial past was originally published on The Sydney Morning Herald.