Doc #22 — NZ Geological and Mineral Resource Atlas

COMPUTED DATA: GEOLOGICAL DATA AND MINERAL MAP

View the Geological Data Tables → — Mineral deposits, critical mineral gap analysis, geothermal resources, and an NZ mineral deposit map.

View the generation script → — Python source code and data sources (Crown Minerals, GNS Science).

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1. IRONSAND (TITANOMAGNETITE)

1.1 Location and extent

NZ’s most strategically important mineral resource. Titanomagnetite ironsand — a heavy black sand containing approximately 57–60% iron and 7–8% titanium dioxide — occurs extensively along the west coast of the North Island, from Kaipara Harbour in the north to Whanganui in the south.⁴ The deposits derive from the erosion of andesitic volcanic rocks in the Taranaki-Taupo volcanic zone, transported to the coast by rivers and redistributed by longshore drift.

The primary mining site is Waikato North Head, near the mouth of the Waikato River, which supplies NZ Steel’s Glenbrook mill via a slurry pipeline. Additional large deposits exist at Taharoa (south Waikato coast) and at numerous other beach and dune locations along the coast.

1.2 Estimated quantity

Total ironsand resources along the west coast are estimated at several billion tonnes.⁵ The Waikato North Head deposit alone contains an estimated resource of approximately 180–250 million tonnes of concentratable ironsand.⁶ At Glenbrook’s historical consumption rate of approximately 1.0–1.4 million tonnes of concentrate per year, the Waikato North Head deposit represents well over a century of supply at post-event production rates. Other deposits extend this further. Ironsand is not a constraining resource for NZ steel production.

1.3 Extraction and infrastructure

Mining at Waikato North Head is by open-cast methods — sand is hydraulically mined, concentrated by magnetic separation on-site, and pumped as slurry through an approximately 18 km pipeline to Glenbrook.⁷ The process is well-established and does not depend on imported equipment for basic operation, though pump components and pipeline maintenance require engineering support.

Taharoa has been mined for ironsand export (shipped to Asian steelmakers) but uses different infrastructure — direct ship-loading via an offshore pipeline.

1.4 Recovery relevance

Critical. Ironsand is the feedstock for NZ’s only steelworks (Doc #89). Without imported iron ore or scrap, ironsand is NZ’s sole pathway to primary steel production. The resource is abundant and accessible. The constraint on steel production is not ore supply but consumables for the Glenbrook process — graphite electrodes, refractories, and coal (see Doc #89).

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2. COAL

2.1 Deposits and types

NZ holds coal deposits in four main regions, spanning all major coal ranks:^{8 9}

West Coast, South Island (Buller and Grey districts): NZ’s highest-quality coal. The Buller coalfield (Stockton, Denniston, Escarpment) produces bituminous coal with low ash and sulfur — historically exported as coking coal and used in steelmaking. The Grey coalfield (Rapahoe, Strongman) produces bituminous and sub-bituminous coal. Total in-ground resource for the West Coast is estimated at approximately 2.5–3.5 billion tonnes, though extractable reserves are a fraction of this due to geological complexity (steep seams, faulting).¹⁰

Waikato, North Island (Huntly area): Sub-bituminous coal, lower energy content than West Coast coal but more accessible — large, relatively flat seams amenable to open-cast and underground mining. The Huntly coalfield has been NZ’s largest single production centre by volume. In-ground resource is estimated at 2–4 billion tonnes.¹¹ Waikato coal has been the primary fuel for Huntly Power Station and a major input for NZ Steel’s Glenbrook operations.

Southland (Ohai, Nightcaps): Sub-bituminous coal, relatively low rank. In-ground resource approximately 1.5–2 billion tonnes.¹² Mining has been intermittent but infrastructure exists.

Canterbury and Otago (various small deposits): Lignite and sub-bituminous coal. Limited production history.¹³

Southland lignite (Eastern Southland): Very large deposits of lignite — low-rank coal with high moisture content. Total in-ground resource estimated at approximately 6–8 billion tonnes, making it by far the largest coal resource in NZ by tonnage.¹⁴ Lignite’s low energy density and high moisture make it impractical for most traditional coal uses without drying or upgrading, but it represents an enormous stored energy resource.

2.2 Total resource

Total NZ coal resource is estimated at approximately 15 billion tonnes in-ground, of which perhaps 1–2 billion tonnes might be economically extractable with existing or readily constructed infrastructure.¹⁵ This represents centuries of supply at any plausible post-event consumption rate.

2.3 Recovery relevance

Critical. Coal serves multiple essential functions under isolation: fuel for NZ Steel’s rotary kilns (Doc #89), feedstock for charcoal production (Doc #102), potential source of coal tar for chemical feedstocks, and backup thermal energy. West Coast bituminous coal is particularly valuable for metallurgical uses. The Waikato sub-bituminous deposits are the most accessible for North Island industries.

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3. GOLD

3.1 Deposits

NZ has three principal gold-producing regions, with a combined historical production of approximately 1,100–1,300 tonnes since the 1850s:¹⁶

Coromandel Peninsula, North Island: Epithermal gold-silver deposits in volcanic rock. The Waihi mine (operated by OceanaGold as of 2025) is NZ’s only large-scale operating gold mine, producing approximately 4–6 tonnes of gold per year from underground operations.¹⁷ The Martha mine at Waihi has produced over 180 tonnes of gold since 1878.¹⁸ Remaining measured and indicated resource at Waihi is in the range of 50–80 tonnes of contained gold, with additional exploration targets in the wider Hauraki Goldfield.

Otago, South Island: Orogenic (schist-hosted) gold deposits and extensive alluvial gold in river gravels. Historical production from the Otago goldfields (1861–1900s) exceeded 200 tonnes, predominantly alluvial. Remaining alluvial gold is present but at low concentrations compared to historical yields. Hard-rock deposits exist at Macraes Flat (operated by OceanaGold), which has produced over 100 tonnes of gold since 1990.¹⁹ Macraes is the largest hard-rock gold mine in NZ by production volume.

West Coast, South Island: Alluvial and hard-rock gold associated with the Alpine Fault zone. Historical production was substantial (Hokitika, Reefton, Ross, Greymouth districts). The Reefton goldfield includes the Globe-Progress mine, which operated until 2016. Remaining alluvial gold is present in river gravels throughout the West Coast but at low concentrations. Hard-rock potential exists in the Reefton area and elsewhere.

3.2 Recovery relevance

Moderate to high. Gold’s primary recovery value is as a medium of exchange and store of value if monetary systems require a physical backing — not as an industrial material. Existing NZ mine infrastructure could continue small-scale production. Alluvial gold recovery requires minimal technology (panning, sluicing) and could employ displaced labour, but yields would be low compared to historical rushes when the richest deposits were mined first. Gold is also useful in small quantities for electrical contacts and corrosion-resistant components.

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4. LIMESTONE AND MARBLE

4.1 Deposits

Limestone (calcium carbonate) occurs widely across NZ:²⁰

Golden Bay / Takaka, South Island: NZ’s largest and highest-purity limestone deposits. The Takaka marble is Ordovician-age crystalline limestone with CaCO3 content exceeding 95%. Holcim (formerly Milburn) operates a major quarry at Ferndale in Golden Bay, supplying cement works. Estimated resource is very large — hundreds of millions of tonnes.

North Island sites: Significant limestone deposits at Te Kuiti (Waikato), Otorohanga, Oamaru (technically South Island — a soft, easily worked limestone), and numerous smaller deposits. The Te Kuiti Group limestones supply cement production in the Waikato.

Other locations: Limestone or marble outcrops in Northland, Hawke’s Bay, Marlborough, Canterbury, and Southland.

4.2 Recovery relevance

Critical. Limestone is the essential raw material for cement production (Doc #97), quicklime and hydrated lime (used in water treatment, mortar, soil amendment, steelmaking flux, and chemical processes), and agricultural lime. NZ’s limestone resources are more than sufficient for all foreseeable recovery needs.

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5. SILICA SAND

5.1 Deposits

Parengarenga Harbour, Northland: NZ’s primary source of high-purity silica sand. The deposit consists of fine-grained quartz sand with SiO2 content of approximately 96–99%, depending on processing. The resource is large — estimated at tens of millions of tonnes.²¹ The sand is bright white and very low in iron contamination, making it suitable for glass production.

Other sources: Lower-purity silica sands occur at various coastal locations (e.g., Pakiri Beach, Northland), but these typically contain higher iron content, resulting in green-tinted glass unless further purified.

5.2 Recovery relevance

High. Silica sand is the primary raw material for glass production (Doc #98) — windows, bottles, laboratory glassware, and optical components. It is also essential for foundry sand (casting moulds — Doc #93). Parengarenga’s high purity makes it NZ’s most valuable silica source. The logistical constraint is transport from a remote Northland site to manufacturing centres further south.

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6. POUNAMU (NEPHRITE JADE) AND SERPENTINITE

6.1 Deposits

Pounamu occurs in the South Island’s West Coast, associated with the Alpine Fault zone — principally in the Arahura River catchment, Marsden, and Cascade areas of Westland and South Westland.²² The stone is a variety of nephrite jade, formed by metamorphism of serpentinite along the plate boundary. Serpentinite itself occurs more widely along the Alpine Fault zone.

6.2 Recovery relevance

Low to moderate for industrial purposes. Pounamu is extremely hard and tough — historically used for tools (toki/adzes), weapons, and ornaments by Maori. Its hardness makes it a potential tool material where steel is unavailable, though pounamu tools are substantially inferior to steel for most applications: they cannot hold a fine edge, are brittle under impact loading, and cannot be reshaped once broken. This application is unlikely to be necessary given NZ’s steel production capability. Serpentinite has some industrial uses as a source of magnesium, though extracting magnesium metal from serpentinite requires calcining the rock (approximately 600–700°C), chemical leaching (hydrochloric or sulfuric acid), and electrolytic reduction of the resulting magnesium chloride — a multi-stage process requiring acid production infrastructure, high-temperature furnaces, and substantial electrical energy.²³

Cultural significance to Maori is substantial and should be respected in any recovery planning involving West Coast mineral extraction.²⁴

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7. COPPER

7.1 Deposits

NZ has very limited copper deposits.²⁵ Historical mining occurred at:

• Kawau Island (Hauraki Gulf): Small copper mine operated in the 1840s–1860s, producing modest quantities from chalcopyrite ore. Deposits are essentially exhausted.
• D’Urville Island (Marlborough Sounds): Minor copper mineralisation, historically prospected but never significantly mined.
• Various small occurrences in Coromandel, Nelson, and Fiordland — all sub-economic by modern standards and small in absolute terms.

7.2 Recovery relevance

This is one of NZ’s most critical mineral deficits. Copper is essential for electrical wiring, motors, generators, transformers, and heat exchangers. NZ currently imports all copper. Existing copper stocks are substantial (the national electrical grid, building wiring, telecommunications cables, plumbing, vehicle wiring) and represent a large recyclable resource, but no new primary copper production is feasible from known NZ deposits. Recycling of existing copper stock and eventual trade with Australia or Chile are the only pathways. See Doc #52 (Wire and Cable Production) for copper conservation and recycling strategy.

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8. SULFUR AND GEOTHERMAL MINERALS

8.1 Sources

NZ’s geothermal areas — principally in the Taupo Volcanic Zone (Rotorua, Wairakei, Kawerau, Ohaaki, White Island/Whakaari) — produce native sulfur and hydrogen sulfide gas.²⁶

White Island (Whakaari): Has the largest known sulfur deposits in NZ — an estimated 6–10 million tonnes of sulfur on the island, mostly in fumarolic deposits and altered rock. Historical sulfur mining operated intermittently from the 1880s to the 1930s, ending after a lahar destroyed the mining operation and killed all workers in 1914.²⁷ Access is hazardous and the island is an active volcano. Quantities are large but extraction is dangerous.

Rotorua-Taupo geothermal zone: Hydrogen sulfide (H2S) is present in geothermal steam at concentrations of approximately 0.1–1% by weight. NZ geothermal power stations already manage H2S as a waste product — it is a nuisance that corrodes equipment and produces odour. Capturing and converting H2S to elemental sulfur is technically straightforward (Claus process or similar) and is already done at some NZ geothermal plants for environmental compliance.²⁸

8.2 Recovery relevance

High. Sulfur is the starting point for sulfuric acid production — the single most important industrial chemical by volume, required for fertiliser (superphosphate), metal processing, chemical manufacturing, and explosives. NZ’s geothermal H2S represents a renewable sulfur source that does not deplete. White Island sulfur is a large but hazardous alternative. Sulfuric acid production from geothermal sulfur should be a medium-term industrial development priority.

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9. CLAY DEPOSITS

9.1 Types and locations

NZ has extensive clay deposits suitable for ceramics and brick production:²⁹

• Halloysite: High-quality white clay occurring at Matauri Bay (Northland) and other Northland sites. NZ halloysite is internationally significant — exported for use in fine ceramics, catalysts, and specialty applications. The Matauri Bay deposit is large (millions of tonnes).
• Kaolin: White-firing clay at various Northland and Waikato locations. Suitable for ceramics and potentially for paper coating.
• Ball clays: Fine-grained clays suitable for pottery and tableware. Various North Island locations.
• Brick clays: Common clays suitable for structural brick and tile production. Widespread across both islands — virtually every region has accessible clay deposits.
• Fireclay: Clay with high alumina content suitable for refractory bricks. Present in association with some coal seams (particularly Waikato and West Coast).

9.2 Recovery relevance

High. Clay products — bricks, tiles, drainage pipes, pottery, refractory linings — are fundamental building materials producible with simple technology (clay + kiln). NZ has more than sufficient clay resources. Fireclay is particularly important for building furnace linings for metalworking (Doc #89, Doc #92, Doc #93). Halloysite is a potential export commodity if trade develops.

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10. PHOSPHATE ROCK

10.1 NZ deposits

NZ has very limited phosphate rock deposits. The most notable is the Clarendon phosphorite deposit in South Otago — a marine sedimentary deposit of modest size, with estimated resources of approximately 5–10 million tonnes at low grade (approximately 10–15% P2O5).³⁰ Small phosphorite occurrences exist at Chatham Islands and in some Northland locations.

10.2 Recovery relevance

Critical deficit. Phosphorus is an essential, non-substitutable plant nutrient. NZ agriculture is heavily dependent on imported phosphate fertiliser — historically from Morocco, China, and the Pacific Islands (Nauru, Christmas Island). Without imports, NZ’s soil phosphorus reserves will deplete over years to decades depending on soil type and farming intensity (Doc #80). The Clarendon deposit could provide limited supplementation but at 10–15% P2O5 grade it requires roughly 2–3 times the mining and processing effort per unit of phosphorus compared to major world deposits (28–37% P2O5).³¹ Bone meal recycling, sewage phosphorus recovery, and guano deposits (offshore islands) are partial mitigations — collectively these sources might supply 10–20% of NZ’s pre-event phosphate application rates, leaving a substantial deficit that constrains agricultural productivity.³² Phosphate is one of the strongest arguments for establishing Tasman trade.

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11. AGGREGATE AND BUILDING STONE

11.1 Resources

NZ has abundant aggregate resources — crusite (crushed rock), river gravel, and sand suitable for concrete, roading, and construction. Greywacke (a hard, durable sandstone) is the most common aggregate source and is quarried throughout both islands.³³ Volcanic rock (basalt, andesite) provides high-quality aggregate in the Auckland, Waikato, and Bay of Plenty regions.

Building stone suitable for dimension stone use includes: Oamaru stone (a soft, easily worked limestone from North Otago, historically used for many South Island buildings),³⁴ Halswell basalt (Canterbury), various granites and schists.

11.2 Recovery relevance

Moderate. Aggregate and building stone are essential but not constraining — NZ has far more than it could use. The constraint is transport and processing energy, not supply.

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12. OTHER MINERALS OF NOTE

12.1 Chromite

Minor chromite (chromium ore) deposits exist in the Dun Mountain ophiolite belt near Nelson.³⁵ Quantities are small and sub-economic by international standards, but chromium is important for stainless steel and some alloy applications. Any NZ chromite production would be very small-scale.

12.2 Titanium

NZ ironsand contains approximately 7–8% TiO2 (titanium dioxide). NZ Steel’s electric arc furnace slag is approximately 20–28% TiO2 — a potentially significant titanium resource already concentrated as a by-product.³⁶ Extracting metallic titanium from TiO2 requires the Kroll process: chlorination of TiO2 to titanium tetrachloride (requiring chlorine gas production, which itself requires salt electrolysis and substantial electrical power), purification of TiCl4 by fractional distillation, and reduction with magnesium metal in a sealed argon atmosphere at approximately 800–850°C. The magnesium must itself be produced by electrolysis. Each step requires dedicated chemical plant infrastructure, high-purity feedstocks, and trained operators — placing metallic titanium production at feasibility [D] for NZ under isolation.³⁷ TiO2 as a white pigment is more feasible to extract via acid leaching of the slag and would be valuable for paint production — a feasibility [C] project requiring sulfuric acid production capability (Doc #116).

12.3 Bentonite

Bentonite clay (sodium montmorillonite) occurs at several NZ locations, including deposits near Porangahau (Hawke’s Bay).³⁸ Bentonite is useful for foundry sand binding (Doc #93), drilling mud, and sealing applications.

12.4 Diatomite

Deposits of diatomaceous earth at various North Island locations (notably near Tokoroa).³⁹ Used as a filtration medium, mild abrasive, and insulation material.

12.5 Zeolites

Natural zeolite deposits in the Ngakuru area (near Rotorua) and other volcanic zones.⁴⁰ Zeolites are useful for water purification, soil amendment, and industrial catalysis.

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13. CRITICAL MINERAL DEFICITS

The following minerals are essential for industrial recovery but absent or insufficient in NZ:

Mineral	Primary uses	NZ status	Mitigation pathway
Copper	Electrical wiring, motors, plumbing	No economic deposits	Recycling existing stock; Australian trade
Aluminium ore (bauxite)	Structural material, electrical conductor	None in NZ	Tiwai Point smelter stocks (imported alumina); Australian bauxite via trade
Phosphate rock	Fertiliser (non-substitutable)	Very limited, low grade	Bone meal, sewage recovery; Australian/Pacific trade
Tin	Solder, tinplate, bearings	None known	Recycling; trade
Zinc	Galvanising, brass, batteries	None known	Recycling; Australian trade
Lead	Batteries, radiation shielding	Very minor occurrences	Recycling (especially vehicle batteries); trade
Rare earth elements	Electronics, magnets, catalysts	None known at economic scale	Australian deposits (Mount Weld); trade
Manganese	Steel alloying	Very minor occurrences	Australian trade; limited alloying alternatives
Nickel	Stainless steel, batteries	None known	Recycling; trade

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14. AUSTRALIAN RESOURCES ACCESSIBLE VIA TASMAN TRADE

Australia possesses one of the world’s most significant mineral endowments. If Tasman trade can be established (Doc #151), the following Australian resources are most relevant to NZ’s recovery needs:⁴¹

Bauxite: Australia holds the world’s largest bauxite reserves — estimated at 5–6 billion tonnes — primarily at Weipa (Queensland), Gove (Northern Territory), and the Darling Range (Western Australia).⁴² Bauxite is the ore for aluminium, which NZ cannot produce domestically once Tiwai Point smelter stocks are exhausted.

Copper: Major deposits at Mount Isa (Queensland), Olympic Dam (South Australia), and numerous other sites. Australia is a major copper producer. Even modest trade volumes could address NZ’s copper deficit.

Phosphate rock: Deposits at Duchess (Queensland) and rock phosphate from Christmas Island (Australian territory). Less significant globally than Middle Eastern or North African deposits but accessible via Tasman shipping.

Rare earth elements: The Mount Weld deposit (Western Australia) is one of the world’s richest rare earth deposits. Processing is complex but Australia has existing capability.

Zinc and lead: Major deposits at Broken Hill (NSW), Mount Isa, and McArthur River (Northern Territory).

Manganese: Groote Eylandt (Northern Territory) is one of the world’s largest manganese producers.

Sulfur: Available as a by-product of Australian base metal smelting, though NZ’s geothermal sources may be sufficient.

Recovery implication: Australia’s mineral wealth is the strongest strategic argument for prioritising Tasman trade development. A single sailing vessel carrying 50–100 tonnes of copper concentrate per voyage — a plausible cargo for a medium-sized trading vessel (Doc #138) — would substantially extend NZ’s electrical infrastructure lifespan. The trade relationship would likely be reciprocal — NZ can offer food, timber, and manufactured goods that Australia may lack under isolation conditions.

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15. DATA SOURCES AND LIMITATIONS

15.1 Primary data sources

• GNS Science: NZ’s Crown Research Institute for geological sciences. Maintains the national geological map database (QMAP), mineral resource assessments, and geothermal research data.⁴³
• NZ Petroleum and Minerals (Crown Minerals): Branch of MBIE responsible for Crown mineral estate management. Maintains the Minerals Permit database and publishes mineral resource assessments.⁴⁴
• NZ Minerals Industry Association: Industry body representing mining companies in NZ.⁴⁵
• Published geological survey bulletins: Extensive historical geological literature from the NZ Geological Survey (now part of GNS Science) and university research.

15.2 Limitations

Resource estimates cited in this document are approximate and based on published data of varying vintage. Several important caveats apply:

• “In-ground resource” figures include material at all depths and grades, much of which may not be extractable with available technology or energy. Economically extractable reserves are typically 5–20% of total in-ground resource.
• NZ’s mineral exploration history is incomplete. Significant deposits may exist undiscovered, particularly in remote areas of the South Island and offshore.
• Quantity estimates for some deposits (particularly coal and ironsand) are reasonably robust, based on extensive drilling programs. Others (minor minerals, small deposits) are based on limited data and should be treated as indicative only.
• Australian resource figures are approximate and based on published national assessments; actual post-event availability depends on the state of Australian infrastructure and governance.

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16. CROSS-REFERENCES

Document	Relationship
Doc #89 — NZ Steel Glenbrook	Ironsand and coal as steelmaking feedstocks
Doc #52 — Wire and Cable Production	Copper supply constraints
Doc #80 — Soil Fertility	Phosphate deficit and soil nutrient management
Doc #93 — Foundry and Casting	Sand, clay, and metals supply
Doc #97 — Cement and Concrete	Limestone supply
Doc #98 — Glass Production	Silica sand from Parengarenga
Doc #92 — Blacksmithing and Forge Work	Coal and iron supply
Doc #102 — Charcoal Production	Coal as feedstock alternative
Doc #151 — Trans-Tasman Relations and Trade	Australian mineral access

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FOOTNOTES

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1. GNS Science (Institute of Geological and Nuclear Sciences). NZ’s primary geological research institution. Maintains national geological maps, mineral resource databases, and geothermal research programs. https://www.gns.cri.nz/↩︎

2. NZ Petroleum and Minerals (Crown Minerals), Ministry of Business, Innovation and Employment. Manages the Crown mineral estate and publishes mineral resource data. https://www.nzpam.govt.nz/↩︎

3. Minerals Industry Association of New Zealand (now known as Straterra). Industry body representing NZ mining and quarrying companies. https://www.straterra.co.nz/↩︎

4. NZ Steel, “About Our Iron Sand,” company publication. Titanomagnetite ironsand is a specific type of iron ore containing ilmenite and magnetite, with approximately 57–60% total iron content and 7–8% TiO2. The west coast North Island deposits are among the largest titanomagnetite ironsand deposits in the world.↩︎

5. Christie, A.B., et al., “Mineral Resource Assessment of the West Coast Region, New Zealand,” GNS Science Report, various editions. Total west coast ironsand resource estimates vary by source but consistently indicate billions of tonnes of material in beach and dune deposits.↩︎

6. Christie, A.B., et al., “Mineral Resource Assessment of the West Coast Region, New Zealand,” GNS Science Report, various editions. Total west coast ironsand resource estimates vary by source but consistently indicate billions of tonnes of material in beach and dune deposits.↩︎

7. NZ Steel operations description. The Waikato North Head mining operation uses a hydraulic monitor (high-pressure water jet) to disaggregate dune sand, which flows as slurry through a series of magnetic separators to concentrate the titanomagnetite. Concentrate is then pumped via pipeline to Glenbrook.↩︎

8. Edbrooke, S.W., et al., “New Zealand Coal Resources,” GNS Science Monograph, Institute of Geological and Nuclear Sciences, 2000. The standard reference for NZ coal geology and resource estimates.↩︎

9. Ministry of Business, Innovation and Employment, “New Zealand Energy Data File,” published annually. Contains coal production and resource data. Total identified coal resource approximately 15.3 billion tonnes (as of recent assessments), including all ranks from lignite to bituminous.↩︎

10. Barry, J.M., et al., “Buller Coalfield,” NZ Geological Survey Bulletins, various dates. West Coast bituminous coal is NZ’s highest rank coal, with gross calorific values of 27–31 MJ/kg and coking properties suitable for metallurgical use.↩︎

11. Edbrooke, S.W., “The Geological Setting of the Waikato Coal Region,” in Geology of the Waikato Region, GNS Science, various dates. Waikato sub-bituminous coal has gross calorific values of approximately 19–24 MJ/kg.↩︎

12. Edbrooke, S.W., et al., “New Zealand Coal Resources,” GNS Science Monograph, 2000. Southland sub-bituminous coal resource estimates based on NZ Geological Survey and GNS Science assessments of the Ohai and Nightcaps coalfields.↩︎

13. Edbrooke, S.W., et al., “New Zealand Coal Resources,” GNS Science Monograph, Institute of Geological and Nuclear Sciences, 2000. The standard reference for NZ coal geology and resource estimates.↩︎

14. Turnbull, I.M., et al., “Eastern Southland Lignite Deposits,” NZ Geological Survey Reports. Estimated total in-ground lignite resource of approximately 6–8 billion tonnes, primarily in the Gore, Mataura, and Pomahaka areas. Lignite calorific value is approximately 10–15 MJ/kg (as-received), roughly half that of bituminous coal per tonne.↩︎

15. Ministry of Business, Innovation and Employment, “New Zealand Energy Data File,” published annually. Contains coal production and resource data. Total identified coal resource approximately 15.3 billion tonnes (as of recent assessments), including all ranks from lignite to bituminous.↩︎

16. Christie, A.B. and Brathwaite, R.L., “Mineral Commodity Report 14 — Gold,” NZ Mining, 2003. Historical NZ gold production from 1852 to present totals approximately 1,100–1,300 tonnes.↩︎

17. OceanaGold Corporation, annual reports and resource statements. The Waihi operation (Martha mine and Correnso underground) produced approximately 4–6 tonnes of gold annually as of recent reporting years. Total historical production from the Martha mine exceeds 180 tonnes since 1878.↩︎

18. OceanaGold Corporation, annual reports and resource statements. The Waihi operation (Martha mine and Correnso underground) produced approximately 4–6 tonnes of gold annually as of recent reporting years. Total historical production from the Martha mine exceeds 180 tonnes since 1878.↩︎

19. OceanaGold Corporation, “Macraes Gold Project,” resource and reserve statements. Macraes Flat in East Otago is a large, low-grade orogenic gold deposit hosted in schist. Cumulative production exceeded 100 tonnes by the early 2020s.↩︎

20. Christie, A.B. and Barker, R.G., “Mineral Commodity Report — Limestone, Marble, and Dolomite,” NZ Mining. Golden Bay limestones are the highest purity in NZ, with CaCO3 content typically 95–98%. Used for cement, quicklime, agricultural lime, and as a flux in steelmaking.↩︎

21. Christie, A.B., “Mineral Commodity Report — Silica,” NZ Mining. Parengarenga Harbour silica sand has SiO2 content of approximately 96–99% and very low iron content (typically < 0.05% Fe2O3 in the best grades), making it suitable for clear glass production.↩︎

22. Beck, R.J., New Zealand Jade, Reed, 1984. Pounamu occurs as boulders and in-situ veins in serpentinite along the Alpine Fault zone. The Ngai Tahu Claims Settlement Act 1998 recognises Ngai Tahu ownership of all naturally occurring pounamu in the Ngai Tahu takiwa (tribal area).↩︎

23. Titanium metal extraction via the Kroll process is described in standard metallurgical references. See Habashi, F., “Handbook of Extractive Metallurgy,” Wiley-VCH, 1997. The process requires chlorine, magnesium, and argon — none of which NZ currently produces at industrial scale.↩︎

24. The Ngai Tahu Claims Settlement Act 1998 vests ownership of pounamu in Te Runanga o Ngai Tahu. Any extraction or use of pounamu requires Ngai Tahu consent. This legal framework should be respected in recovery planning.↩︎

25. Brathwaite, R.L. and Christie, A.B., “Mineral Commodity Report — Copper,” NZ Mining. NZ has no significant copper deposits. Historical production from all NZ copper mines combined is estimated at less than 1,000 tonnes of contained copper — negligible by international standards.↩︎

26. Giggenbach, W.F., “Geothermal Mineral Deposits,” various publications. NZ’s geothermal systems in the Taupo Volcanic Zone are predominantly liquid-dominated (hot water) rather than vapour-dominated, but hydrogen sulfide is present in the steam fraction of most geothermal fluids.↩︎

27. Johnston, D.M., et al., “White Island (Whakaari): Volcanic Hazard and Risk Assessment,” GNS Science Report. Sulfur mining at Whakaari operated from 1885 to 1933, with the 1914 lahar killing all 12 workers on the island. The deposits remain large but access is extremely hazardous.↩︎

28. Contact Energy and Mercury NZ geothermal operations documentation. H2S abatement at NZ geothermal power stations typically involves converting H2S to elemental sulfur or sulfate via chemical oxidation. The Claus process (partial oxidation of H2S to sulfur) is used industrially worldwide and could be adapted for NZ geothermal sulfur recovery.↩︎

29. Christie, A.B., “Mineral Commodity Report — Clays,” NZ Mining. NZ Halloysite from Matauri Bay has been exported for specialty ceramic applications. The deposit is estimated at several million tonnes.↩︎

30. Watters, W.A., “Clarendon Phosphorite,” NZ Geological Survey Records. The Clarendon deposit is a marine phosphorite of Miocene age, with P2O5 grades of approximately 10–15% — significantly lower than the 28–37% typical of major world phosphate rock producers.↩︎

31. Watters, W.A., “Clarendon Phosphorite,” NZ Geological Survey Records. The Clarendon deposit is a marine phosphorite of Miocene age, with P2O5 grades of approximately 10–15% — significantly lower than the 28–37% typical of major world phosphate rock producers.↩︎

32. Estimate based on NZ’s pre-event phosphate fertiliser application of approximately 400,000–500,000 tonnes of superphosphate per year (Ministry for Primary Industries data). Bone meal, sewage sludge, and guano deposits on offshore islands collectively represent a small fraction of this volume. Specific recovery rates depend on collection infrastructure and processing capability.↩︎

33. Aggregate & Quarry Association of New Zealand data. NZ quarries approximately 25–30 million tonnes of aggregate per year from over 700 quarry sites. Greywacke is the dominant aggregate type.↩︎

34. Oamaru stone is a bioclastic limestone of Oligocene age, quarried from the Ototara Formation in the Waitaki district. Its softness when freshly quarried (Mohs hardness approximately 3) and subsequent hardening on exposure make it a historically important NZ building material. Based on GNS Science QMAP geological data.↩︎

35. Johnston, M.R., “The Dun Mountain Ophiolite Belt,” Geological Society of NZ Miscellaneous Publication. The Dun Mountain-Maitai terrane contains ultramafic rocks with minor chromite concentrations, historically prospected but never economically mined.↩︎

36. NZ Steel technical documentation. Glenbrook EAF slag contains approximately 20–28% TiO2, making it one of the most concentrated titanium-bearing waste streams in the world. Several research programs have investigated titanium recovery from this slag, but none have reached commercial scale.↩︎

37. NZ Steel technical documentation. Glenbrook EAF slag contains approximately 20–28% TiO2, making it one of the most concentrated titanium-bearing waste streams in the world. Several research programs have investigated titanium recovery from this slag, but none have reached commercial scale.↩︎

38. Smectite clays including bentonite occur at several NZ locations. The Porangahau deposit in Hawke’s Bay has been characterised as a sodium bentonite suitable for industrial applications. Based on GNS Science mineral occurrence records.↩︎

39. Christie, A.B., “Mineral Commodity Report — Diatomite,” NZ Mining. NZ diatomite deposits are associated with volcanic lake sediments, principally in the central North Island.↩︎

40. Christie, A.B., “Mineral Commodity Report — Zeolites,” NZ Mining. NZ natural zeolites (primarily clinoptilolite and mordenite) occur in altered volcanic ash deposits in the Taupo Volcanic Zone.↩︎

41. Geoscience Australia, “Australia’s Identified Mineral Resources,” published annually. Australia’s mineral resources are among the world’s largest: first or second globally in bauxite, iron ore, gold, zinc, lead, and various other minerals. https://www.ga.gov.au/↩︎

42. Geoscience Australia, “Australia’s Identified Mineral Resources,” published annually. Australia’s mineral resources are among the world’s largest: first or second globally in bauxite, iron ore, gold, zinc, lead, and various other minerals. https://www.ga.gov.au/↩︎

43. GNS Science (Institute of Geological and Nuclear Sciences). NZ’s primary geological research institution. Maintains national geological maps, mineral resource databases, and geothermal research programs. https://www.gns.cri.nz/↩︎

44. NZ Petroleum and Minerals (Crown Minerals), Ministry of Business, Innovation and Employment. Manages the Crown mineral estate and publishes mineral resource data. https://www.nzpam.govt.nz/↩︎

45. Minerals Industry Association of New Zealand (now known as Straterra). Industry body representing NZ mining and quarrying companies. https://www.straterra.co.nz/↩︎