Coal is a combustible rock formed from the altered remains of ancient vegetation laid down in peat swamps. It is mainly composed of organic matter (compounds of carbon), moisture and minerals. The transition from peat to coal (coalification) occurs over millions of years as peat is buried and consolidated by the weight of overlying sediments.
Three factors determine the properties of coal:
As coal becomes buried more deeply, it goes through a sequence of changes in rank: from peat to lignite, sub-bituminous coal, bituminous coal, semi-anthracite, and anthracite. This process results in irreversible changes in the chemical and physical nature of the coal, and there can be considerable variation within a coalfield. Geological age does not affect rank.
From peat to bituminous coal there is a progressive loss of water and a proportionate increase in carbon. Lignite and sub-bituminous coal is relatively soft, with a brown, earthy appearance – these are often known as brown coals. Higher-rank coals are blacker, shinier, and have a higher proportion of carbon.
As the rank increases, so does the heat (or calorific value) given out by the coal when it burns. It is difficult to make a fire from lignite because the moisture content is so high. Sub-bituminous coal burns well, and bituminous coal burns fiercely.
New Zealand coals have characteristics that distinguish them from coals found in other countries. Most of the world’s coals were formed in great swamps during the Carboniferous period, about 300–350 million years ago. New Zealand coals are much younger, having been formed mainly in the late Cretaceous and Tertiary periods, 30–70 million years ago, from more-evolved vegetation types containing flowering plants. Because the original vegetation is different, New Zealand coals have some unusual properties, giving them high value for specialised purposes.
When coal burns, the ash that remains consists mainly of clay minerals, quartz, and sulfur compounds (mainly pyrite). Most New Zealand coals have an ash content of less than 4%, which is lower than most Carboniferous coals. A few seams have an exceptionally low ash content – less than 1%.
Government coal surveys and exploration by mining companies have established that New Zealand has an estimated 16 billion tonnes of in-ground coal. However, 80% of this is lignite in Otago and Southland. Of the balance, much of the easily won coal is gone. The remaining amount that could be recovered is relatively quite small and depends on geological, engineering, economic and environmental constraints.
North Island coalfields are located in Northland, Waikato and northern Taranaki. Most known areas of sub-bituminous coal in Northland have been worked out, and the last mine closed in 1955.
Thirteen coalfields, extending from Drury (30 kilometres south of Auckland) to Mangapēhi (20 kilometres south of Te Kūiti), are geologically grouped as Waikato coalfields. In these, there are 2 billion tonnes of in-ground coal. However, much of this is in seams that are too deep to mine. In 2020, opencast mines at Maramarua and Rotowaro were the only Waikato mines still working.
Waikato coals are all sub-bituminous, laid down in the Eocene and Oligocene periods. Seams in the north of the region generally have low to medium ash and low sulfur contents, while seams in the south have medium to high ash and sulfur contents. The main seam is typically 3–10 metres thick, but reaches 20 metres or more in parts of the Huntly and Waikare coalfields.
Coal measures is a name for coal-bearing sedimentary rocks, which include sandstone, mudstone and conglomerates as well as coal seams. Coal measures mined in New Zealand are generally a few tens to several hundreds of metres thick, and between 10 and 75 million years old.
There are five coalfields in northern Taranaki, of which the Mōkau coalfield near the west coast is the largest. Previous mining was on a small scale, and there has been no production since the last mine, in the Waitewhena coalfield, closed in 1990. In-ground resources amount to 380 million tonnes of sub-bituminous coal, but this is unlikely to be economically mineable.
The South Island’s West Coast region contains New Zealand’s only bituminous coals. Some have unusual properties that are in demand in international coal markets. There are 13 coalfields of various sizes between Greymouth and Seddonville (40 kilometres north of Westport). The Buller, Greymouth, Īnangahua and Reefton coalfields are the most economically important.
While there are large quantities of in-ground coal remaining in the region, most of the easily-won coal has been mined. Over three-quarters of resources are in the Greymouth coalfield (mostly underground) and Buller coalfield (mostly opencast), but how much is mineable depends on coal prices, land access and a resumption of underground mining. After an explosion at the Pike River mine in 2010 which killed 29 men, the government decided that there would be no further mining in the area, which has been added to the Paparoa National Park.
One of the unusual features of the West Coast coalfields is that bituminous coal is found at high altitudes. In the 1940s, geologist Harold Wellman recognised that this was due to a complex two-stage geological history. Maximum burial occurred about 35 million years ago, then the deeply buried basins were lifted, so that they are now preserved in the mountains – a process later named inversion tectonics.
There are two main types of coal measures on the West Coast: late Cretaceous to earliest Tertiary Paparoa coal measures, and Eocene Brunner coal measures. Both Paparoa and Brunner coalfields contain seams up to 20 metres thick. Paparoa coals are characterised by low ash and sulfur contents. Brunner coals have similar properties but with varying sulfur contents.
West Coast coals are almost all bituminous, with a small deposit of anthracite at Fox River. Their properties see them valued as blending coals on world markets.
The bulk of New Zealand’s coal resources are lignites in the south of the South Island. Over 7 billion tonnes of mineable lignite resources have been proven in Otago and Southland, enough to provide a significant proportion of New Zealand’s energy needs for a long period if needed.
Otago coalfields include very large lignite deposits in Central Otago, the Kaitangata coalfield south of Dunedin, and several smaller coalfields. Central Otago lignites are in seams up to 90 metres thick and typically have 40%–50% in-ground moisture and low to medium ash and low sulfur contents.
The eastern Southland lignite fields are comparable to other large deposits in the world and are, by far, New Zealand’s biggest fossil fuel energy resource. They form extensive, multiple seams up to 18 metres thick, and typically have 40%–65% in-ground moisture and low to medium ash and low sulfur contents.
The Ōhai coalfield in central Southland has seams up to 23 metres thick containing sub-bituminous and bituminous coals, generally with low ash and sulfur contents.
It is said that Tainui Māori knew that waro (coal) had heating properties and used it for cooking. The first European use was probably at Shag Point on the Otago coast, where whalers used coal to heat trypots for rendering blubber.
The settlers of the 1840s, knowing that Britain’s industrial revolution had been fuelled by coal, quickly prospected for it. Thomas Brunner recorded coal in the Grey River in 1848, and by 1860 most of the main fields had been discovered – in that year Julius Haast noted the potential of the Denniston plateau in Buller.
The first New Zealand mine was established in 1849 at Saddle Hill, Dunedin, and over the next 20 years a number of small working mines were set up. Most were mere holes in the ground employing a handful of people, often on a seasonal basis, and catering for the local market. In the south, mining began at Kaitangata in 1858, at Green Island in 1861, and at Shag Point the next year. The Malvern Hills mine in Canterbury was worked from 1862, and in Golden Bay there was a small mine at Collingwood from 1868. In the North Island the largest operation, which started in 1865, was at Kawakawa.
In the 1870s promoters imagined a thriving coal industry as the basis for New Zealand’s industrial future. Coal was essential to Julius Vogel’s expansionist immigration and transport policies. Trains were fired by coal, and increasingly, ships’ sails were replaced by coal-powered steam engines. During that decade, coal became New Zealand’s fifth-largest import, mostly from Newcastle in New South Wales. With such demand, mining attracted investors.
In the heady days of the 1870s there was much unrealistic boosterism. For instance, in 1873 the Albion Coal Company attracted £60,000 from investors as far away as Auckland for a mine at Ngakawau in Buller. Investors were not so happy when they learnt that the coal was friable and disintegrated in the open air, and a bar made the Ngakawau River impassable.
The first field with major potential was at Brunner in the Grey River valley. Mining had begun there in a small way in 1864. Once a railway to Greymouth replaced barges in 1876, and a new bridge across the Grey River was completed the next year, the Brunner mines were able to expand. A new breakwater to counteract the harbour bar also helped. By 1888 the field was producing a third of New Zealand’s coal output, which had tripled from 10 years before. Coking and brickworks developed as spin-offs. Coke was made by baking coal to remove the volatile matter and water to produce a smokeless fuel. Four years later another deposit was opened further up the valley at Blackball.
Transport improvements were the key to Buller’s success. The quality of the coal on the Denniston plateau, some 600 metres high, had been quickly recognised. But it was the completion of the cable railway known as the Denniston incline in 1879, and the branch rail line to Westport, that made mining the field possible. The incline gained a local reputation as the ‘eighth wonder of the world’. It was just over 1.5 kilometres long, with a very steep gradient.
In 1889 HMS Calliope, a British warship, took on Westport coal at Wellington before heading for Apia in Samoa, where there were six other warships in port. When a tropical cyclone drove the ships shoreward, the Calliope fired its engines and proceeded out to sea. When it returned, it was the only ship still afloat. Calliope’s engineer attributed its survival to the quality of the coal. This made Westport coal’s reputation, and the British Admiralty stationed a coal-purchasing agent in Westport.
Denniston was funded by a group of Dunedin businessmen, including James Mills of the Union Steam Ship Company. By 1887, through its majority ownership of the Westport Coal Company, the Union Company had effective control of the Denniston mine in addition to its buy-out of the Brunner mines the previous year. This ‘southern octopus’ monopolised the West Coast fields, which by 1896 were producing over half of New Zealand’s coal.
In Otago, the Kaitangata mines employed over 140 men in 1896 (compared with 315 at Denniston), and at Huntly in Waikato, where mining had begun in 1876, there were over 100. Many small operations sprang up. In 1896 there were 163 mines, but only 20 employed more than 20 men. By 1900 New Zealand was producing over a million tons of coal annually, a six-fold increase since records began in 1878, and over eight times the amount being imported. Coal had become the country’s main energy source.
From 1900 to 1914 New Zealand coal production more than doubled to 2.25 million tonnes, a figure it would not consistently exceed until the Second World War. This dramatic increase was due to the demands of steamships and railways, the export-driven growth of dairy factories and freezing works, and the development of municipal gasworks that used coal to produce domestic gas.
The most spectacular growth came in Buller, where the Westport Coal Company developed major deposits at Millerton and Stockton. By 1914, one-third of New Zealand’s coal came from the Buller mines.
The Grey River fields saw falling production in the Brunner area, but in 1901 Richard Seddon’s government created State Coal Mines to challenge the Union Steam Ship Company’s coal monopoly and improve safety. The first state mine was at Seddonville in Buller. The state’s Point Elizabeth mine, established near Rūnanga in 1904, revived mining in the Grey River valley. By 1914 the area was producing a quarter of the country’s coal, and the West Coast, in all, contributed three-fifths.
Further south, the Kaitangata field remained static (contributing less than 13% in 1914) as Dunedin lost its economic pre-eminence. Production expanded in the Huntly area, where dairying and the industrial and domestic demand of Auckland provided strong local markets. Production quadrupled between 1900 and 1914 to reach 15% of the national total. During the First World War a new bridge across the Waikato River opened up areas for mining in the hills to the west – at Pukemiro, Glen Afton and Rotowaro.
In the interwar years the West Coast suffered as ships turned to oil in place of coal. By the mid-1930s the Waikato fields were producing as much coal as the West Coast fields. The economic depression encouraged a revival of small-scale mining as miners, laid off from the large operations, developed cooperatives and reopened abandoned workings. By mid-1930 there were several hundred such operations.
The outbreak of war in 1939 gave a new value to coal. From 1942, coal mining became an essential industry and miners were prohibited from changing jobs. The Labour government began taking over pits, especially if they looked like failing. By 1942 all the mines in the Grey River valley and Waikato had been nationalised. By the late 1940s state-owned mines were producing over half of New Zealand’s coal, and in 1948 coal deposits were nationalised – a decision reversed by the new National government two years later.
Another important development in this period was the beginning of opencast mining on a substantial scale. In this method, coal is mined from the surface rather than from underground workings. At the start of the war only 2% of coal was mined in this way. By 1945 the figure was over 16%. In 1960, when coal production reached a post-war peak of over 3 million tonnes, 37% came from opencast mines. By 1979, when production had fallen to under 2 million tonnes, opencast mining contributed 69%.
The fall in the 1960s and 1970s was particularly severe on the West Coast, partly because bituminous coal, once the fuel of ships and trains, was no longer in demand, as ships had switched to oil and the railways were in decline. In addition, gas was increasingly being replaced by hydro-electric power and eventually by Māui natural gas, while household use of coal in 1972 was a quarter of the 1949 level. Twelve significant mines closed between 1967 and 1974.
There was evidence of decline in coal mining everywhere – the number of mines fell from 216 in 1953 to 78 in 1973, while the number of miners fell from over 5,000 to about 1,500, almost half of whom were aged over 45. In the same period, the Grey River valley workforce fell to a quarter, the Buller workers to a third. Denniston, which once had a population of 1,308, had only four people living there in 1981.
A slow revival in coal mining from the early 1980s picked up dramatically in the 1990s, driven mainly by coal exports and electricity generation. In 2003 the national production was over 5 million tonnes, double the 1990 figure. In 1987 State Coal Mines was transformed into a state-owned enterprise, Coal Corp, which by 2003, rebranded as Solid Energy, was producing 80% of the nation’s coal. Solid Energy was broken up and sold in 2017.
In 1983 the dual-fuel 1,000MW Huntly power station was commissioned, and it initially ran mainly on gas. However, as gas supplies tightened in the early 2000s, it used over 1 million tonnes of coal a year, sourced from several Waikato mines and some imports. Running at maximum capacity on coal, the Huntly power station could use over 3 million tonnes of coal a year. Its output has now been partly replaced by renewables.
In 2020, the second major domestic market was the steel mill at Glenbrook, south of Auckland. This used iron sand from the west coast of the North Island and coal from Waikato to produce about 600,000 tonnes of flat-steel products for domestic and export use.
The dairy industry, one of New Zealand’s biggest export earners, used coal extensively, mainly in the South Island. The cement, timber, food-processing and health sectors also used coal, either for direct heat supply or cogeneration. Cogeneration produces both heat and electricity, and increases the overall efficiency of converting coal to energy by up to 90%.
Some New Zealand coals have properties that are in demand internationally, and a modest coal export industry developed following trial shipments to Japan in 1976. All export coal came from mines on the West Coast of the South Island. Solid Energy was the major exporter, shipping 2.14 million tonnes in 2004. Most exports were of premium-quality coking coal for steel making, sent mainly to Japan, and also to India, South Africa, China and Brazil. In 2020, New Zealand was still a small contributor in the international coal market (less than 0.5% of all coal shipped).
In the early 2000s there were about 45 coal mines in New Zealand, although some produced only a few thousand tonnes a year. About 40% of production was from the Waikato region, where the two major mines were Rotowaro (an opencast mine) and Huntly East, the only underground mine in the North Island. The Glenbrook steel mill and the Huntly thermal power station were the main users of Waikato coal.
Because underground mining leaves part of the seam still in the ground, some modern opencast mines work in areas previously mined underground.
The most spectacular growth in mining in the early 21st century came on the West Coast. At Stockton in the Buller coalfield (the country’s largest operation, with an annual output of over 1.5 million tonnes) a 2.2-kilometre aerial ropeway was used to bring coal down from the Stockton plateau. Near Greymouth, the Strongman 2 underground mine was productive for nine years (1994–2003), and was replaced by the Spring Creek underground mine. The use of high-pressure water-jet cutting and hydraulic transport of coal improved the productivity and safety of underground mining. By 2003 the West Coast area was contributing close to half of New Zealand’s coal production, whereas in 1990 its share was less than 30%.
The one area where growth in mining was limited was in the lignite fields of Southland, New Zealand’s largest coal resource.
Almost all 19th-century mining was underground, and colonial men, used to a footloose, independent life, did not easily adjust to underground mining. Those who took up mining in New Zealand tended to be immigrants – at first from the copper- and tin-mining areas of Cornwall and Devon, and then from coal-mining areas in Northumberland, Durham, Yorkshire and Wales. Many brought with them traditions of trade unionism and Methodism. In the early 20th century a number came from the Australian fields, while the expansion of the Waikato fields after the First World War attracted Māori workers into the mines.
Given their backgrounds, it is unsurprising that the early miners used traditional techniques to extract coal. At first this involved picks and shovels. Seams of coal were mined using the ‘bord and pillar’ method – sections were extracted leaving pillars to hold up the roof, then the pillars were partly removed as the miners retreated towards the entrance.
Mechanisation was slowly introduced from the 1900s. Because mining conditions varied so much between coalfields, no one method was useful everywhere. Compressed-air machinery was used to varying degrees. In the later 20th century, high-pressure water-jet cutting was introduced in some West Coast mines. Coal flowed out in water directly from the face, whereas in conventional mining the coal was drilled, blasted, and loaded into tubs or carried on conveyors.
Tommy Pinn started at the Strongman mine in 1941 and retired 46 years later. In 2003, as the mine finally closed, he noted: ‘Boy they’ve got a good number today, all the miner was doing was sitting behind this big machine pushing buttons, in a matter of minutes 2 metres of coal was cut from a place about 15 feet wide by 10 feet. It would take the best part of two or more days to do that in my time, after you did all the timbering, boring and blasting. Then we had to shovel the whole lot all out by hand!’ 1
Besides the hewers at the coal face, there were many other workers underground – those hauling the coal, pumping water, looking after the ventilation, and trimming the lamps. In the 19th century their conditions of work were often appalling. At first, the same areas were used as eating places and latrines. When excrement cans were provided, they were often placed in old workings where toxic firedamp (methane gas from coal) collected. Most mines before the First World War did not provide bathhouses and it was a long, dirty and often wet walk back home. Above ground, men worked as loaders, screening the coal, and as blacksmiths, carpenters and engine men.
On the West Coast, work was erratic because the river ports were often closed by bad weather. On many days the mines did not open.
Modern mining is increasingly opencast, and by the early 2000s only two major underground mines remained (Huntly East and Spring Creek). The last underground mine in New Zealand closed in 2017.
Opencast mining involves removing overburden from the coal seam using motor scrapers or by blasting harder cover rocks. The debris is removed by heavy equipment, including draglines, shovels, bulldozers, front-end loaders and trucks. Opencast mining generally recovers 90% or more of the coal seam, compared with 25% to 75% from underground mining. The deepest opencast mine in New Zealand is at Rotowaro.
From the 1990s it became normal practice to restore mine sites as near as possible to their pre-mining state.
Traditional mining was highly dangerous. There were three main causes of accidents: rock falls, often when the pillars were mined; explosions, most frequently occasioned by firedamp (methane gas given off by coal), which was usually ignited by a miner’s naked flame; and tubs travelling on the haulage system knocking men over.
There was a high level of injury and death, but there were few large-scale tragedies. At Denniston in the 10 years from 1881 to 1891 there were 10 deaths and 35 serious injuries. Of the 141 men killed nationwide between 1900 and 1914, 98 were individual deaths.
New Zealand mining has seen a number of mass tragedies:
Miners might also fall sick from miners’ phthisis or pulmonary tuberculosis, and they often suffered ailments such as boils or poisoned hands. It is little wonder that absenteeism was high.
It could be tough being married to a coal miner. Caroline Denson’s first husband died at Kaitangata in 1879. Her second, Harry, perished in the Brunner explosion 17 years later.
Following the Kaitangata disaster in 1879, the Mines Department was given power to inspect mines, and this provision was progressively strengthened. But even 40 years later, inspections were sporadic and depended on a strong union to be effective. From 1886 mine managers had to be certified.
The rise of opencast mining brought greater levels of safety, and there was growing intolerance of levels of injury that had once been accepted as part of a miner’s life. By the early 21st century, the mining industry had its own codes of practice. Following the 2010 Pike River explosion, the government set up Worksafe New Zealand to be responsible for all workplace safety issues, with a designated High Hazards Unit covering industries such as mining and petroleum exploration.
Mining permits are administered by the Ministry of Business, Innovation and Employment. Environmental regulation is managed through the resource consent process administered by local government.
The structure and conditions of the coal-mining industry meant that industrial relations were difficult. From the 1880s the industry was controlled by a small group of the country’s capitalist élite. Many of the miners came from Britain, bringing strong traditions of trade unionism with them. Working conditions were dangerous. The men lived in isolated communities where it was easy to organise resistance and create a sense of togetherness. Many mining towns became centres for socialist activism and teaching. The result was a series of strong unions and a pattern of strikes. The unions included:
Most coal mines were in isolated places, and on the West Coast they tended to be in the damp Grey River valley or on the foggy, cold Denniston plateau. Often miners did not anticipate living there permanently and were loath to invest in housing. The mine owners skimped on single men’s huts. The results were unlined, damp shacks, unsanitary conditions, and often no more than a kerosene tin for washing.
Overcrowding was common. Samuel Hurst Seager, a Christchurch architect, was appalled when he investigated mining centres in 1918. He described ‘barbarous conditions’ and housing ‘dreary in the extreme’. 1 Housing for Māori miners in the 1940s was appalling, with ‘flattened oil drums for weatherboards’. 2
Isolation, physical hardship, poor housing and the British origins of many miners bred a distinctive culture. It became accepted that on ‘pay Saturday’, once a fortnight, men would take the day off. Drinking was widespread. A 1919 Board of Trade report claimed that alcohol consumption was twice as great in mining areas as elsewhere.
Brunner had six hotels, Denniston three. The hotel was often the only warm, comfortable place to meet and chat, and it was the venue for activities as diverse as darts and boxing bouts. Gambling on these pursuits and on horses and dogs was widespread. Yet mining communities also included non-drinkers, often of a Methodist background, some of whom encouraged their fellows into socialist reading cells.
Ettie Rout described the socialist miners when editing the Maoriland Worker: ‘They live in gloomy valleys, they work in holes in the earth, they live on the West Coast where it is nearly always raining, where 80% of the men drink, drink, drink, in a wild endeavour to forget who they are and where they live.’ 3
Mining and its distinctive character helped enrich New Zealand society. In men like Paddy Webb and Bob Semple the country gained some unique public figures – both were Australian-born radicals who became members of the 1935–49 Labour government.
Several New Zealand novels have evoked the experience of coal mining – Bill Pearson’s Coal flat (1963), Eric Beardsley’s Blackball 08 (1984), and Jenny Pattrick’s The Denniston rose (2003). Mervyn Thompson’s one-man play Coaltown blues, which he performed 114 times between 1984 and 1988, evokes growing up in a West Coast mining community.
In 2019 coal contributed about 6% of New Zealand‘s primary energy supply, mainly for steel making, food processing and a decreasing amount of electricity generation. It seems likely these proportions will increase. At times of low hydro and wind generation, non-renewable sources are used to help meet the gap between supply and demand. Both coal and gas have been used in recent years, but reduced gas supply has seen increasing use of coal-fired generation, mainly from imported coal.
The steel mill at Glenbrook uses about 800,000 tonnes of coal each year to smelt ironsand. The dairy industry uses a similar amount, almost entirely in the South Island, where there is no gas supply for process heat. The same applies to other South Island industries, including food processing. These uses of coal can be expected to continue for some time.
Coal from some West Coast mines, mainly Stockton, is exported via the port of Lyttelton. Mining coal for export is dependent on good prices for coking coal and access to the remaining sources of suitable coal.
The South Island lignite resource has the potential to be used as a petrochemical feedstock if necessary.
Coal is widely perceived to be a polluting fuel, but in developed economies this perception is largely a hangover from the belching smokestacks of the industrial revolution. Pollution from smoke and soot was largely under control by the end of the 1970s, and by the 2000s environmentally acceptable levels of sulphur dioxide and nitrogen oxide emissions were readily achievable at ever-reducing costs.
The main concern surrounding the use of coal is its contribution to atmospheric concentrations of carbon dioxide – a cause of potentially adverse climate change.
Coal cannot be burnt without producing carbon dioxide. Because coal is such an important energy source worldwide, massive efforts are being made by many countries to find ways to reduce or eliminate emissions. These focus on replacing coal with gas or, increasingly, with renewable sources of energy.
Crawshaw, Norman. The first wave: a history of the early days of coal in Buller. Westport: N. Crawshaw, 1999.
Macfie, Rebecca. Tragedy at Pike River Mine: how and why 29 men died. Wellington: Awa Press, 2013.
Ministry of Energy. The coal industry of New Zealand. Wellington: Government Printer, 1974.
Richardson, Len. Coal, class and community: the united mineworkers of New Zealand, 1880–1960. Auckland: Auckland University Press, 1995.
Sherwood, A. M. An outline of the geology of New Zealand coalfields. New Zealand Geological Survey Record 7. Wellington: New Zealand Geological Survey, 1986.
Wood, Brian. Coal Gorge and the Brunner suspension bridge: a heritage and environmental study. Greymouth: B. Wood, 2004.