The Dilemma of Dolomite Use

Forest and Bird, Issue 302, 1 November 2001, Page 21

The Dilemma of Dolomite Use

The chairman of OMYA, Dave Martin, says that dolomite quarrying has been steadily increasing over the last few years, both for agriculture and for industry. One hundred percent of the rock quarried from Mt Burnett is used. Around 80 percent is crushed to a dust for agricultural fertilizer, to increase magnesium and calcium levels. Soil-magnesium levels nationwide have been steadily declining since forested land was cleared for farming. Today most farmland either has a low magnesium content or magnesium has leached from the earth, with a noticeable decline over the past 20-30 years. Magnesium content in soils is important for dairy farming. It doesn't enhance grass growth but acts as a preventative for grass staggers, a magnesium deficiency which can kill cows. Waste rock from the mine is used for river protection. Waste rock has "a slightly higher than normal silica content", which means lower levels of magnesium and calcium. The percentage of dolomite used in agriculture fluctuates annually depending on What the market wants. ‘If someone's doing a protection job, or some roadworks, and they want some large rock in a hurry that can consume quite a lot, says Dave Martin. ‘Mt Burnett ‘waste rock" has been used to create the Seaview Marina at Petone, various flood-control stopbanks, roadworks, sea walls in Golden Bay, and 14,500 dolomite stone panels as the exterior cladding of Te Papa.