Much of the following notes are taken from the document "Historic Assesment: Onoke Ballast Pit" by Maria Butcher (April 2011) which was commissioned by the Department of Conservation - www.doc.govt.nz/pagefiles/72064/onoke-heritage-assessment.pdf.
It is not known exactly when the Onoke Ballast Pit opened. It may have been around 1878, when work on the Whangarei to Kamo railway section of railway began. This short length was one of the earliest railways in Northland, built to transport coal mined at Kamo to the wharf at Whangarei however reference in the Northern Advocate show it was operating in 1893.
Scoria ballast was moved from the quarry to the railway using a self-acting incline which was one of several safety hazards noted with the Ballast Quarry operation. In 1898 the Northern Advocate reported that a skip of ballast accidentally got loose, descending the incline at a "terrific" speed, and bouncing across the railway into the paddock below.
The track from the road is slowly being cleared and is, at the current time, easy to follow through the regenerating bush to the main junction where the incline track heads off to the left. A short distance down the incline sits Boiler No. 41 which powered the steam engine and crusher plant. Both the engine and crusher were recovered when the quarry was officially closed about 1938 however the boiler was deemed not worth salvaging and remains on site. Boiler No. 41 is a horizontal fire tube type, mounted on a pair of concrete platforms. The cylinder is largely intact with the panels being connected by older style lap joints; three sides of the fire box have been removed exposing the stay bolts and ends of the flues. Some minor preservation work was carried out on the boiler (cleaned and treated with Fishoilene) in 2010/2011.
Please re-hide the cache carefully as the reserve is often visited by local children. GPS co-ordinate accuracy does suffer due to the terrain.