The Waiareka Valley has a history of coal mines, and deposits were first discovered in the 1850s.
The Ngapara coal mine was opened in 1878 by James Nimmo, and operated until the 1960s.
Road Metals has operated its quarry for about three years and knew there was a coal deposit there.
It quarries for sand and Ngapara gravel, used for cement and roading.
The quarry is on a hill face approaching the Ngapara township.
The company recently cut a new face in the quarry and discovered the extent of the seam.
Mr Kelcher said the low-grade coal was being shifted and stored.
Some of it had been sent away for analysis of its fertiliser content.
At this stage, the company was not sure what to do with it, Mr Kelcher said.
The company's quarry borders land owned by Holcim (New Zealand) Ltd at Ngapara.
Holcim has resource consent for an open cast mine on its land, so it can mine coal to fuel its proposed cement plant, near Weston.
