Commodities, Inventory & Collectibles

How to Underwrite a Mining Project or Mineral Reserves

Underwrite a mining project by valuing reserves from a qualified technical report and testing cash flow against conservative commodity prices and costs. The metrics that matter most are proven and probable reserves, ore grade and metallurgical recovery, all-in sustaining cost relative to price, reserve life beyond debt maturity and initial capital intensity.

What makes mineral reserves underwriting different

A mine extracts a finite orebody, so value depends on how much economically mineable material exists, its grade, how much metal processing recovers, operating costs and commodity prices. Reserves reported under recognized standards by a qualified person form the basis for valuation, while resources that have not been converted to reserves are less certain. Costs depend on mining method, strip ratio, haul distances, processing route, energy, water and labor. Risks include grade variability, metallurgical surprises, construction overruns, permitting delays, community opposition, tailings and closure liabilities and commodity cycles. Development projects carry construction and ramp-up risk that producing mines have already worked through.

Lenders finance producing mines or fully permitted construction projects with solid reserves and a competitive cost position. They size debt to cash flow at conservative prices, require completion tests before releasing sponsor guarantees, and want a meaningful reserve tail after the loan matures. Equity investors underwrite exploration upside, mine life extensions, expansion and leverage to higher commodity prices. Equity often values inferred resources and district potential that lenders ignore. Streaming and royalty investors sit between the two, buying a share of production or revenue and underwriting the orebody and operator over the full mine life.

Key metrics

Proven and probable reserves

Reserves define the economically mineable base used for valuation and debt sizing.

Ore grade and metallurgical recovery

Grade times recovery determines metal produced per ton processed and is the most sensitive driver of revenue.

All-in sustaining cost (AISC)

Shows the mine's position on the industry cost curve and how far prices can fall before cash flow turns negative.

Lenders commonly favor mines in the lower half of the industry cost curve for the commodity.

Strip ratio

Waste tons moved per ton of ore drive open pit mining cost and can rise as the pit deepens.

Reserve tail

Remaining reserve life after debt maturity gives lenders room to extend if production underperforms.

Mining lenders often look for reserves extending well beyond final loan maturity, sometimes framed as a share of total reserves left after repayment.

NPV and IRR at downside prices

Shows whether the project still creates value and services debt in a weak price environment.

How to underwrite it, step by step

Review the technical report and the qualified person's reserve and resource estimates.
Assess geology, drill spacing, grade continuity, metallurgical testwork and recovery assumptions.
Evaluate the mine plan, strip ratio, processing route and operating cost build-up.
Review permits, environmental and social impact studies, water rights and community agreements.
Model cash flow at base and downside price decks with cost and grade sensitivities.
Have an independent engineer review the construction budget, schedule, contractor and contingency.
Structure debt with completion tests, reserve tail requirements, hedging and reserve accounts.

Due diligence checklist

Technical report with reserve and resource statements
Feasibility study
Metallurgical testwork results
Mine plan and life-of-mine production schedule
Permits and environmental and social impact assessments
Water rights and land access agreements
Community and government agreements
Offtake contracts for concentrate or metal
EPC or construction contracts and budget
Closure, reclamation and tailings management plans

Key risks and mitigants

Grade or recovery below estimates

Rely on independent technical review, adequate drill density and pilot-scale metallurgical testing.

Commodity price decline

Size debt to conservative price decks and require hedging of part of early production.

Construction overruns and delayed ramp-up

Require completion guarantees, contingency, cost overrun facilities and a completion test before guarantees fall away.

Permitting or community opposition

Diligence permit status, social license and community benefit agreements before funding.

Tailings, environmental and closure liabilities

Quantify closure costs, review tailings design and require reclamation bonding.

Typical financing and deal structure

Mining projects are financed through project finance loans, corporate revolving facilities for producers, streaming and royalty agreements, offtake prepayments, convertible notes and equity. Project loans typically include completion tests, sponsor completion guarantees, debt service reserve accounts, mandatory hedging, cash sweeps and covenants on reserve tail and coverage. Streams provide upfront capital in exchange for the right to buy a share of future production at a low fixed price, while royalties take a percentage of revenue or net smelter return. Export credit agencies may support financing tied to equipment and offtake. Equity comes from mining companies, specialist funds and public markets, often in several rounds before construction.

Red flags

Reserves based on outdated or non-compliant technical reports.
Metallurgical testwork incomplete or not representative of the orebody.
AISC places the mine in the upper part of the industry cost curve.
Unresolved permitting challenges or community conflicts.
Debt maturity close to the end of reserve life.

Frequently asked questions

How are mines valued?

Mines are usually valued with discounted cash flow models built on reserves, the production schedule, operating and capital costs and commodity price assumptions. Investors cross-check with value per unit of reserves and resources against comparable companies. Lenders focus on cash flow from proven and probable reserves at conservative prices and ignore most exploration upside.

What is all-in sustaining cost?

All-in sustaining cost measures the total cost to produce a unit of metal, including site operating costs, royalties, sustaining capital, reclamation accretion and corporate overhead, but excluding growth capital. It shows how a mine compares with peers on the cost curve and how resilient its cash flow is if commodity prices fall.

What is the difference between mineral resources and reserves?

Resources are concentrations of minerals with reasonable prospects for eventual economic extraction, classified as measured, indicated or inferred. Reserves are the portion of measured and indicated resources shown to be economically mineable through detailed studies that apply mining, processing and cost factors. Lenders size debt to reserves, not resources.

What is a streaming agreement in mining?

A streaming agreement gives a mining company an upfront payment in exchange for the right to buy a fixed share of future production, often a by-product metal, at a low fixed price. It funds construction without traditional debt covenants and gives the streamer exposure to mine life, production volumes and price over the long term.

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Educational content, not investment, credit, legal or tax advice. Benchmarks are common practitioner rules of thumb and vary by lender, market and cycle.