Quarrying & Mining Magazine

Exporting Central Otago schist

DENISE MCNABB explains how an Otago aggregate resource has hit a nerve with overseas markets.

China calling

Last year a Chinese buyer visited most of Central Otago’s 10 or so licensed quarries in the Upper Clutha and other parts of Central Otago to canvass interest about shipping bulk schist to China.
Glen Dennison operates a quarry on State Highway 6, near the Arrowtown turnoff dedicated to cutting stone for nearby Millbrook Resort and another quarry in the Gibbston Valley supplying domestic and international markets. He recently bought a large Chris Cutter rock splitter so he could keep up with orders.
He was one of the quarry operators who received a visit from the Chinese businessman who was sourcing grey rock.
“He was tyre kicking and wanted the rock raw and basically for nothing to process back in China.”
Like other operators spoken to by Q&M, he sent the man packing.
He has not exported to China yet, but said there were big opportunities.
“With coal mining in its twilight years, I see rock exports as an opportunity to create employment.”
Glen says the Chinese used a different process to New Zealand to cut stone and replicate rocks on a large scale using concrete.
“We will end up selling a lot of product to the Chinese, mainly for paving.”
Tauranga-based Island Stone placed an order for 10 tonnes of samples from Glen Dennison’s Gibbston Valley quarry recently for a wealthy client in Hollywood, Los Angeles. That volume may increase to 25 tonnes Island Stone’s owner/manager, Peter Flint says.
His Tauranga business has a factory in Cromwell that cuts stone anywhere between 20mm and 60mm for cladding.
The company spent two years rigorously testing its lightweight stone cladding system (LSC) against international benchmarks, including the adhesive it used, before it committed to a contract to clad parts of the exterior of the Hilton Hotel in Queenstown.
The use of New Zealand stone for cladding might be still in its infancy, but it’s growing steadily, Peter says.

WHEN PROSPECTORS FLOCKED to Central Otago in the 1860s’ gold rush, schist rock dominating the landscape was a logical material for fencing and for sturdy cottages and buildings to keep bleak winters at bay.

Today, thanks to revolutionary advances in cutting and cladding processes, schist is shaping up as a new goldmine for the region’s quarry operators.

Schist, a metamorphic rock created 150 million to 200 million years ago by tectonic upheaval, has long been sought after as a material for homes, entranceways paving, walls, pillars, gates and chimneys, but due to its weight and the extraction and cutting processes it has been at the higher end of cladding choices.

As it is found in only a handful of countries, its relatively unique nature and its high rating by stonemasons has fuelled exports of the rock from New Zealand of any note since the early 80s with orders coming from overseas clients wealthy enough to pay the expensive freight on top of rock prices. 

The attraction for the stonemason and the customer alike lies in schist’s robustness; it’s easily split at right angles, is smooth in nature, and has myriad colours, ranging from slate grey to dark chocolate, orange, cream, gold and silver.

It’s also streaked in varying colours from copper to charcoal or white, and the crystallised mica and quartz trapped in its veins sparkles in the sunlight. 

Over the past couple of decades, Australia has been the predominant importer though orders there and elsewhere have been sporadic and not exceptionally large, say Central Otago quarry operators spoken to by Q&M.

Game changer

The advent of a wall-cladding system using sawn schist cut as thin as 15mm, but usually around 40-50 mm thick and applied in a similar manner to tiling has been the game changer.

By using exceptionally strong glue to adhere the sawn stone to wooden walls without causing warping, or to other materials, such as fibre cement, concrete or certain brick veneers and using ventilated cavity systems, up to three-quarters of the weight of a conventional stone laying project using mortar can be taken out of the equation. This means much larger volumes can be shipped overseas at a cheaper price than previously.

Sawn stone cladding systems have been around for a while now, but with the growing popularity of schist for homes, buildings and landscaping, particularly in China, orders for thinly sliced, lightweight stone cladding have gained momentum.

Veteran quarryman George Ellis’ Hydestone was a Kiwi pioneer in the development of a cladding building system for 150 mm sawn stone.

After extensive testing and encompassing new building regulations such as weather tightness in the early 2000s, the company sought and received exclusive Building Research Association of New Zealand (BRANZ) approval for the process that has since been distributed all over the country.

Hydestone is currently seeking BRANZ approval for its cladding system for the thin sawn stone of 40-50mm it sells because it sets a standard that is recognised in both Australia and New Zealand.

George branched into stonework and quarrying, sourcing schist from a 55-hectare quarry in Hyde in 2002 after separating out his transport business so he could focus on quarrying and the rock cutting operation at his plant in the Dunedin suburb of Green Island.

“By sawing the stones into thin slices and gluing them to backing boards before attaching them to the exterior of a home, the former height restriction for stone walls of 2.3 metres was no longer an issue,” he explains.

George is amazed how much interest his company’s website receives from overseas.

“I never thought we would be sending stone to Tahiti.”

Even more surprising was an order for six containers of Central Otago schist for a customer on the Isle of Man five years ago.

George is still scratching his head over that one because the Shetland Isles is not far up the map from the Isle of Man and it’s full of metamorphic rock, similar to Central Otago’s schist.

Like most Central Otago quarry operators, Hydestone’s overseas orders are predominantly for residential homes in Australia or the United States.

George recalls a burgeoning schist export business back in the 80s in spite of the weighty orders and high freight costs.

“We sent a lot of split stone and building stone back then to Melbourne, Brisbane, Noumea and parts of California for residential cladding in those days,” he says.

Then in the late 80s, the value of the Kiwi dollar climbed so high, exporting became an uneconomic proposition.

A trickle of wealthy foreign buyers who could sustain the hefty freight charges continued to stoke a tiny but sporadic export market, but when the global financial crisis hit a decade ago it virtually brought rock exporting to a standstill, Suzanne Grant says.

She and her husband, Dave run Alexandra Stone alongside their winemaking business.

“Orders are coming back.”

In November the company sent two containers of rock to Sanctuary Cove on Australia’s Gold Coast for a home, and three shipments to Sydney for a house in the well-heeled suburb of Vaucluse.

“It has become cheaper to send rock to Australia than to Auckland,” Suzanne says, citing the high costs of rail freight here, exacerbated by the Kaikoura earthquake disaster destroying sections of the track.

Lucy and Grant Middendorf run Cluden Stone Quarry near Tarras, and they too have received overseas orders, including one for 10 tonnes of rock to Australia recently, and an order for rocks to Japan. If a client wants their rock thinly cut then they pass that to someone skilled at doing that. The quarry keeps them more than busy.

Central Otago’s schist is generally dispatched overseas from Port Chalmers.

It does not have GST on it, but there are other costs, including mining royalties paid to the government.

I talked to the owners, who were shy about revealing their export costs, citing commercial sensitivity, but material was around $1200 a tonne to export to Australia a decade ago, and the price has been rising slowly since then.

George Ellis says the growing level of international interest in sawn Central Otago schist has prompted his firm to open Hydestone NZ Distributors in the United States back in April, employing local agents to sell the Kiwi stone.

“The US is big. We sent 40 tonnes of stone to California for a house.”

The company also has agents in Australia.

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