Limestone is a rock composed mainly of lime (calcium carbonate – CaCO3), almost always formed from shelly material. Some limestones are very fine-grained, originally being a limey ooze on the sea floor, but in other rocks large shell fragments can be seen. Limestone is widespread in New Zealand, and formed mainly in late Eocene to Oligocene time, 25–40 million years ago when much of the New Zealand region was submerged beneath the sea.
The hardness of limestone depends on how deeply it has been buried. Softer rocks such as Ōamaru stone have been compacted, but can still be carved and cut with a saw. Most other limestones have been more deeply buried. The calcium carbonate has crystallised in the pore spaces to form a hard, dense rock that can be polished. When limestone is deeply buried and heated it recrystallises so that the original shelly material cannot be recognised, and it is then called marble.
Limestone called marble
Most limestones are harder than Ōamaru stone, and are much more difficult to work. They have, therefore, been mainly used for decorative facing stone. Although the term marble is often used for such rocks, the original shells are still visible, and they are technically limestone.
Whāngārei marble is the commercial name for pale-coloured limestone quarried near Whāngārei and widely used for facing stone. It takes a high polish, and has been used for decorative facing panels in several buildings. Similarly, Hanmer marble is the commercial name for a dense limestone with a pinkish-brown colour found in the Waiau valley, north Canterbury. The distinctive colour is due to the presence of small amounts of volcanic ash.
Tākaka marble
Tākaka marble is a true marble that occurs in the area around Tākaka, and has been worked from a number of quarries on Tākaka hill or in the nearby Holyoake valley since the early 1900s. Impurities vary from place to place, so each quarry produces distinctive coloured marble, ranging from white to pink or grey, and locally almost black.
The new Kairuru quarry, in the Holyoake valley, was the main producer in 2005 – mainly building panels and tiles. The rock is a coarse, crystalline marble with orange veins and irregular staining. The old Kairuru quarry, a little further down the hill, produced the grey marble used in Wellington’s Parliament Buildings.
Naming stones
Different quarries sometimes give their own names to the rock they produce, even if it is similar to rock produced nearby. Tākaka marble has also been called Nelson marble and Caanan marble. All these names are from the same area of marble that geologists call Mt Arthur marble.
Takaka Hill: The Marble Obstacle.
To the settlers in the region, Takaka Hill was a major, if not awesome, obstacle between two valuable regions – the cramped and land-hungry settlement of Nelson, and the promising lower reaches of the valleys of the Takaka and Aorere Rivers.
The topography of the Takaka Hill is classic karst, named after a similar marble structure near Trieste in northern Italy, and formed by the dissolving of rocks such as limestone, dolomite and gypsum.
This process leaves funnel-shaped tunnels called dolines, and sink-holes and caves around the non-soluble rock in the structure.
The first non-Maori to traverse the hill is thought to have been Charles Heaphy, the artist and inveterate explorer aboard the New Zealand Company’s (which founded Nelson, Wellington and New Plymouth) first immigrant ship Tory. He later earned the first Victoria Cross for gallantry awarded to a British colonial soldier during the Waikato Land Wars in the 1860s. Heaphy, who was farming in Nelson at the time, crossed the Takaka massif in 1843.
He was later part of two great exploratory journeys of the South Island, the first with a Maori guide called Kehu, and William Fox up the Buller River, and the second with Thomas Brunner through south Westland.
At first the only way for the settlers to get to what are now the towns of Takaka and Collingwood was by ship around Separation Point, where the massif juts out into Golden Bay.
The road not only opened up the Takaka and Aorere valleys for farming, but also allowed a marble mine to be established on the hill-top at Kairuru, 10 kilometres from Riwaka, which developed a name for quality stone used in the construction industry around the turn of the century.
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.
The Government Architect, John Campbell, specified Takaka marble for the construction of Parliament Buildings from 1911, because it was strong and it could be polished to a bright creamy lustre.
A 10.4 kilometre tramline was formed to cart the big blocks of marble down to Sandy Bay, north of Kaiteriteri, from where they were shipped to Wellington.
By the time Parliament Buildings was completed in 1922, 5000 tonnes of marble had been quarried from Kairuru.
The road not only opened up the Takaka and Aorere valleys for farming, but also allowed a marble mine to be established on the hill-top at Kairuru, 10 kilometres from Riwaka, which developed a name for quality stone used in the construction industry around the turn of the century.
Takaka marble is still available today, though from the Kairuru quarry in the Holyoake Valley, up the hill from Riwaka.
The modern road still follows the course of the one completed in 1900, and though it is less than 60 kilometres from Riwaka to Takaka, the winding and precipitous route takes a good hour to drive.
It’s a spectacular drive though, with features like the eerie karst formations on the Canaan Plateau on the top, and Harewood’s Hole, once thought to be the deepest in the country, hidden away by massive cliffs, but both accessible to motorists.
The drive from the top down to Takaka covers only about 10 kilometres, but it’s a series of savage switchbacks, and the steepness of the descent that cuts speed to a minimum.
Some 200 years on, the taipo, the goblin, still bellows up through the caverns and tunnels deep in the mountain, but it’s with a benign voice now, and its song is for travellers rather than refugees from Te Rauparaha.
The modern road still follows the course of the one completed in 1900, and though it is less than 60 kilometres from Riwaka to Takaka, the winding and precipitous route takes a good hour to drive.
Marble Mountain for good reason.
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 – it is almost solid marble. State Highway 60 weaves a tortuous 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.
The Earthcache - "Kaka Beak"
At the indicated coordinates is a two-piece artwork made of Takaka marble entitled "Kaka Beak", hence the cache name. It was created in 2010 by local artist Bruce Mitchell. To log your find of this Earthcache please send me your answers for the following questions. Q4 may require some research online.
QUESTIONS
1. What colours are prevalent in the artwork ?
2. Compare the feel of upper treated marble versus lower untreated stone. Describe the difference to the touch.
3. Estimate the widths of the different bands of colours. What do you think caused the different colours?
4. The by-product of marble; the crushed calcium carbonate (whites) was often used elsewhere. Agricultural lime is one use, name 3 further uses.
Once you complete the Earthcache requirements you can post your find without delay, as per the guidelines. You will also need to verify your find by sending me an email providing answers to the questions. This can be through the message centre or via email linked in my profile.
Credit for original source material; February 18th, 2016 Charles Fairbairn Contractor, Historical Contractor.