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Agriculture, poultry farms, glass making and even topping your morning cereal – lime is a versatile if not healthful mineral as ALAN TITCHALL finds out while visiting one of the country’s historic quarries.
Takaka Hill is almost solid marble. State Highway 60 weaves a torturous path over this hill, cutting through ancient craggy lime and marble formations coloured a grey/black with algae. As the road nears the Ngarua Caves below the summit on the Nelson side, it passes an old green building that houses the crushing plant of the Ngarua Lime quarry, owned by Ravensdown. Ngarua Lime quarry sits on precipitous farmland a little further up the hill from a more famous quarry, Kairuru, which gained national prominence in 1911 when it was chosen for marble used in the construction of the new Parliament Buildings in Wellington, and again in the 1990s when the building was renovated. It wasn’t just the construction industry that sought Takaka marble; the crushed calcium carbonate (whites) ended up as in cosmetics, household cleaners, toothpaste, paint, glass, paper manufacturing (up to 40 percent of paper is calcium carbonate), and even the health supplement industry. Ngarua used to produce about 35 different products from its marble but in recent years New Zealand marble, as a building material and calcium carbonate additive, has been competing against cheap imports from Australia and China. Ngarua’s resource, these days, is mostly crushed into a high-quality lime for the agricultural industry. There’s a certain amount of chip for the landscape industry, large catchment stone and even small, 6mm chip for poultry farms where it is mixed in with chook food to harden their egg shells. “Ninety percent of what we do is agricultural lime,” says manager Mark Simkin who has worked at Ngarua for 18 years, starting there when his father Barry Simkin leased the property, and including the period when Omya operated the quarry before the Swedish company sold it to Ravensdown five years ago.
“Now there’s just the two of us,” as the operation has been simplified down to handle the local agricultural and aggregate market he says. In the meantime, there’s a local who pops under the radar every month for a couple of kilos of lime dust to sprinkle on his breakfast cereal as a calcium supplement. Ravensdown owns the land and minerals of 14 hectares of this high grade resource with further rights to access additional resource. Takaka marble varies in colour from black to white with everything in between. “We have very little over-burden, you just go straight into the resource,” says Mark. Only the ‘dyke’, bands of material pushed together when the marble was formed from limestone by heat and pressure in the earth’s crust, is a waste material. Mark says that this dyke is either very soft and turns to sand or is so hard it will literally ‘ping’ out of the crusher. Closest to the crushing buildings is the Glass Quarry, named so because it originally supplied lime to a large glass works in Christchurch. With no iron content, the calcium produced crystal clear glass. The farm slopes away very steeply with the road connecting the lower quarries hugging the hill sides with nervous drops on one side.
“We did loose a compressor a number of years ago from the back of a truck when the tow bar broke, and that was interesting watching it slowly disappear back down the road and over the edge.” With the ridges solid marble, erosion is not a problem for the roads or for maintenance but the haul from the bottom quarries does add to the costs. The roads also restrict the size of the excavator used; no more than 40 tonnes however, there’s not much call for anything bigger than 20 tonnes, says Mark. The older quarries such as Kairuru are only opened up two or three times a year for white chip or large rock, because of the 30 minute round trip to the crusher. “That’s expensive when you are only getting around $20 a tonne for the product,” Mark says. Recent Government inquiries to the old marble may mean more activity in the lower reaches, although the most recent interest in the Kairuru site was from Hollywood who sent a team of set designers to convert it into an outdoor stage for a biblical film on the resurrection of Christ. The project was pulled at the start of the global recession.
Near the entrance to Ngarua are the green painted crusher and storage buildings. Three original concrete surge bins from the 1930s are still in use and about to go nowhere soon. “The concrete was carried up in buckets and poured into boxing to create 18-metre high, 200mm thick walls full of reinforced steel,” observes Mark. They survived the 7.8 magnitude Murchison earthquake in 1929. The 40-year old Goodwin Barsby crusher was designed to 120mm, so Mark says they have to “wound it up as tight as they can get it” to crush down to 60mm. “It slows down production but we can still crush 120 tonne with two operators – more than enough to survive the day.”
“We budget around 20,000 to 25,000 tonne a year.” As with all lime quarries, the fine dust from the pulverised marble is ever present – as claggy, grey mud in winter and a white coating during summer. “The mud is the most annoying and makes the roads slippery,” says Mark. “I prefer the dust. It blows away and we have a good extraction system with the crusher. Nor does it affect your health in any way. It’s just pure calcium and that just makes your bones nice and strong.” It is also a dust Mark has grown up with. “I love this job and I wouldn’t be here if I didn’t. I remember as a six-year-old going to work with my father and sitting in dump trucks all day long. It was great. Boys and toys basically.”
Q&M Vol.7 No.4 August-September 2010 |
The massive Takaka Hill, dividing Nelson and Golden Bay at the top of the South Island, is better known to locals as Marble Mountain for good reason.
Mark says that when he first started at Ngarua the quarry produced twice as much ‘white’ product to agricultural lime with some nine staff.
Mark says they have never lost a truck in his memory, although the roads were built for small Bedford trucks not the 30-tonne dumpsters used today.
The old Kairuru quarry site is black with aged algae, but you can still see the sheer rock faces where the slabs were cut by hand – drilled with a chisel hit by a sledge hammer and rotated a quarter of turn with every hit. The rock was then spilt along its natural flaws with a feathered wedge. The marble for the first Parliament building was transported in massive 10 tonne blocks via a tramline down the steep hillside for over 10 kilometres to Sandy Bay, from where it was shipped to Wellington. By the time the Parliament Buildings were finished in 1922, some 5000 tonnes of Takaka marble had been quarried. The marble was again used in Wellington for the Massey Memorial and features in the Beehive built in the 1970s.
And the fortunes of the quarry are entwined with those of the farming community with a good year producing 28,000 tonne.