Guide
How to read a rare earth project: exploration, PFS, DFS, permit, construction
A rare earth project's stage is how far it has been proven: exploration finds mineralization, a resource estimate sizes it, a scoping study tests it, a pre-feasibility study (PFS) picks a plan, a feasibility study (DFS) supports financing, and permits, financing and construction turn it into a mine. Each stage proves something specific and leaves other things open.
The stage tells you how much weight a headline number deserves. This directory labels each mine as producing, development, exploration or historic: 1 is producing, 5 are in development and 7 are in exploration. A development project has a defined resource and feasibility, permitting or financing under way, but no commercial rare earth output.
Verified through Oct 1, 2026
At a glance
- Key studies
- Scoping study or PEA, pre-feasibility study, feasibility study
- Standards
- SEC S-K 1300, Canada's NI 43-101 and the JORC Code
- Resource or reserve
- Only a PFS or feasibility study can support a reserve
- Directory labels
- Producing, development, exploration, historic
- Next guide
- How to read resource estimates
- Producing mine
- 1Mountain Pass
- Projects in development
- 5Resource defined; studies, permits or financing under way
- Projects in exploration
- 7No feasibility-grade resource
- Average US mine lead time
- 19 yearsS&P Global, cited by OSTI
What are the stages of a rare earth project, from exploration to production?
A rare earth project moves through exploration, a resource estimate, a scoping study or preliminary economic assessment, a pre-feasibility study, a feasibility study, permitting and financing, construction and ramp-up. Each stage proves more and costs more. The ladder shows what each proves, what it leaves open and which US projects sit there now.
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Exploration
Trenching, drilling and sampling to find and outline mineralization. It proves that rare earths are present and at what sample grades. It does not prove a resource, and an exploration project may be curtailed if results do not justify more work (USGS).
Output Drill and assay results
US projects now
- Exploration: Sheep Creek
- Exploration: Lemhi Pass
- Exploration: Diamond Creek
- Exploration: Silicon Ridge
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Resource estimate
A qualified person estimates tonnes and grade in measured, indicated and inferred categories. It says what is in the ground with reasonable prospects of economic extraction. It is not a reserve and does not show that mining will pay.
Output A technical report with a resource table
US projects now
- Exploration: La Paz JORC, 2021
- Exploration: Bokan Mountain Apr 2026
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Scoping study or preliminary economic assessment (PEA)
A first economic test of the resource, called an initial assessment under S-K 1300, a PEA under NI 43-101 and a scoping study under JORC. It may rely partly on inferred resources and cannot support reserves. It shows whether to go further, not that the project will work.
Output A study with a first NPV and capital cost
US projects now
- Development: Halleck Creek scoping study, 2025
- Development: Round Top PEA
- Development: Brook Mine PEA and conceptual study
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Pre-feasibility study (PFS)
A comprehensive study of a range of options that fixes a preferred mining method, an effective processing method and a plan to sell the product, with a financial analysis. It can support a probable reserve. It is less detailed than a feasibility study.
Output A PFS report and, if justified, reserves
US projects now
- Development: Halleck Creek due Q3 2026
- Development: Brook Mine expected 2027
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Feasibility study (DFS)
Detailed designs and costs, with a detailed financial analysis, good enough to support an investment decision or project financing. Terms such as definitive or bankable feasibility study mean the same. It does not by itself finance or permit a mine.
Output A feasibility report
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Permitting
Environmental review, approval of a plan of operations or permit to mine and, where thorium or uranium is present, radioactive materials licensing. It runs alongside the studies and can take longer than they do.
Output Permits and a record of decision
US projects now
- Development: Bear Lodge FAST-41, to Mar 2028
- Exploration: Sheep Creek Forest Service, decision est. Jul 2027
- Development: Halleck Creek permit filing late 2026
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Financing and decision
Equity, loans and government support are arranged and a construction decision follows. Lenders hire independent reviewers to check the feasibility study.
Output A financial close and a construction decision
US projects now
- Development: Elk Creek EXIM loan in review; construction start targeted Dec 2026
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Construction and ramp-up
Build, commission and bring output to the planned rate. Ramp-up can be smooth or can fail if grades are lower than expected or the process does not work as planned (USGS).
Output A commissioned operation
US projects now
- Development: Brook Mine groundbreaking Jul 2025
- Development: Elk Creek underground portal under way
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Production
Rare earths are mined or processed for sale. The directory labels this status producing.
Output Concentrate or oxide for sale
US projects now
- Producing: Mountain Pass
Marker: ExplorationDevelopmentProducing
Stages follow the USGS account of how a rare earth mine is developed, with study definitions from the SEC's S-K 1300, the JORC Code and Canadian securities regulators. See the guide to resource estimates.
How do the stages map to the status labels used in this directory?
The directory uses four project statuses. Exploration means drilling or sampling with no feasibility-grade resource. Development means a defined resource with feasibility, permitting or financing under way. Producing means rare earths are mined or processed for sale. Historic means a known occurrence with no current program.
| Stage | Directory status | Definition used here | US entries now |
|---|---|---|---|
| Exploration and early resource estimates | Exploration | Drilling or sampling; no feasibility-grade resource, or no rare earth resource estimate yet. | Bokan Mountain, Sheep Creek, Lemhi Pass, Diamond Creek, La Paz, Colosseum, Silicon Ridge |
| Scoping, PFS, feasibility, permitting and financing | Development | Resource defined; feasibility, permitting or financing under way; no commercial rare earth output. | Brook Mine, Round Top, Halleck Creek, Bear Lodge, Elk Creek |
| Construction and ramp-up of a plant | Plant building | A plant under construction or commissioning. | Plants are listed on the map and the company pages. |
| Production | Producing | Mining or processing rare earth material for sale today. | Mountain Pass |
| No current program | Historic | Known occurrence in USGS data without a current development program. | Not tracked as projects; see historic deposits. |
A project can sit between two stages, for example Bokan Mountain has a 2013 PEA but is labeled exploration because it has no feasibility-grade resource or schedule. The labels follow the directory's methodology.
What is the difference between a scoping study, a PFS and a DFS?
A scoping study or PEA is a first economic test that may rely partly on inferred resources and cannot support reserves. A pre-feasibility study picks a mining method and processing route and can support probable reserves. A feasibility study, also called a DFS or bankable study, adds detailed designs and costs to support financing.
| Study | Other names | What it must show | Inferred resources | Can it support reserves? | Confidence |
|---|---|---|---|---|---|
| Scoping study | Initial assessment (S-K 1300); preliminary economic assessment or PEA (NI 43-101) | Reasonable prospects for economic extraction, or potential viability. JORC calls it an order of magnitude study and requires a cautionary statement. | May be included under conditions: S-K 1300 and NI 43-101 allow inferred resources in the economic analysis of an initial assessment or PEA if conditions are met, and JORC requires the share to be stated. | No | Lowest |
| Pre-feasibility study | PFS; preliminary feasibility study | A preferred mining method or pit configuration, an effective processing method and a plan to sell the product, with a financial analysis. | Not in the economic analysis: S-K 1300 bars inferred resources from assessments of viability, and NI 43-101 bars them from a PFS-level analysis. | Yes: probable reserves, and proven ones from measured resources | Higher than scoping, lower than feasibility |
| Feasibility study | DFS; definitive, bankable, full or final feasibility study | Detailed assessments of all modifying factors and a detailed financial analysis, enough to support an investment decision or project financing. | Not in the economic analysis | Yes | Highest |
Definitions are from 17 CFR 229.1300 (S-K 1300), the JORC Code (2012), NI 43-101 and CSA Staff Notice 43-307. The three systems follow the CRIRSCO template in their core definitions, though the SEC rule differs from the CRIRSCO-based codes in some respects.
How long does each stage take, and what does it cost?
Durations are rarely published stage by stage. The USGS puts a new rare earth mine in its slowest class, seven years or more before production, and US mines average about 19 years to begin operation (S&P Global, cited by OSTI). US rare earth projects carry capital costs of about $300M to $1,600M, and costs can rise between studies.
- Lead time 19 years The average time before a US mine begins operation, from S&P Global figures cited by OSTI.
- USGS class Seven years or more The USGS analysis of mine development places a new rare earth mine in its slowest class, because of complex metallurgy and limited ways to enter the market.
- Capital $300M to $1,600M The range of life-of-mine capital across US rare earth projects, by size, processing steps and infrastructure (OSTI).
- Cost drift Elk Creek: $1.14B to $1.85B NioCorp's 2022 feasibility study put initial capital at $1.14B for three products; the 2026 study puts it at $1.85B for eight, up 62%.
- Ramp-up 2 to 12 months, or longer Recent US metal mines took 2 to 12 months to ramp up, and some mines have failed at this stage because grades were lower than expected or the process did not work as planned (USGS).
What should I check when a company announces a milestone?
Check five things: which study it is and under which standard, who signed it, how much of the resource is inferred, whether processing, offtake and financing are included, and whether a number is company-reported. A scoping study is not a feasibility study, and a letter of interest is not a loan.
- 1. Which study? A scoping study cannot support reserves Halleck Creek's 2025 after-tax NPV of $558M comes from a scoping study, so it is a first test, not a feasibility result.
- 2. Which standard? A named qualified person S-K 1300 (SEC filers), NI 43-101 (Canada) and the JORC Code (Australia) each require a qualified or competent person with at least five years of relevant experience.
- 3. How much is inferred? Inferred is the least certain La Paz's JORC resource is 35.2 Mt indicated and 135.4 Mt inferred, so about 79% is inferred. Inferred resources cannot be used to assess economic viability under S-K 1300.
- 4. What is missing? Permits and money Elk Creek has a 2026 feasibility study and its major permits, but still needs project financing before full construction.
- 5. Who says so? Targets are not results First-production dates are company targets, and a non-binding EXIM letter of interest is not a loan. This directory labels both.
Which US rare earth projects are at which stage today?
One project, Mountain Pass, is producing. Elk Creek has a 2026 feasibility study and awaits financing, Round Top expects its feasibility study in Q4 2026 and Halleck Creek expects a pre-feasibility study in Q3 2026. Brook Mine and Bokan Mountain have preliminary or conceptual studies, and the rest are in exploration.
| Project | Status | Latest study | Next milestone |
|---|---|---|---|
| Mountain Pass | Producing | SEC technical report summary with proven and probable reserves (Dec 31, 2025) | Heavy rare earth (Dy and Tb) output expected later in 2026 |
| Brook Mine | Development | Fluor preliminary economic assessment (Jul 2025) and a conceptual study (Jul 2026) | Interim revised economics by end of 2026; pre-feasibility study in 2027; first production targeted 2031 |
| Round Top | Development | Preliminary economic assessment; the feasibility study is in progress | Definitive feasibility study due Q4 2026; commercial production target 2028 |
| Halleck Creek | Development | Scoping study (2025) with a JORC resource | Pre-feasibility study targeted Q3 2026; permit-to-mine filing late 2026 |
| Bear Lodge | Development | Technical report summary with measured and indicated resources for Bull Hill (Mar 2024) | Federal permitting scheduled to finish Mar 2028 (FAST-41) |
| Elk Creek | Development | NI 43-101 feasibility study (2026) | Construction start targeted Dec 2026, subject to EXIM financing |
| Bokan Mountain | Exploration | Preliminary economic assessment (2013) and a resource update (Apr 2026) | No mine schedule; Ucore focuses its near-term US effort on a Louisiana processing complex |
| Sheep Creek | Exploration | No resource estimate; exploration plan under Forest Service review | Forest Service review of a reduced plan filed Jun 12, 2026; decision estimated Jul 2027 |
| Lemhi Pass | Exploration | No modern resource estimate | Permitting and drill targeting for 2026 and beyond; no resource estimate |
| Diamond Creek | Exploration | Surface sampling and drilling results (Jul 2026); no resource estimate | Bulk sampling and mineralogical studies in H2 2026; no resource estimate |
| La Paz | Exploration | JORC resource (2021); no economic study | Historic-data and metals-potential review continues through 2026 |
| Colosseum | Exploration | A gold bankable study (May 2026); no rare earth resource estimate | Court hearing on stay motions Oct 26, 2026; injunction in force since Aug 10 |
| Silicon Ridge | Exploration | A company-reported estimate with no rare earth grade, and a preliminary economic assessment | Further drilling and studies; no rare earth grade published for the maiden estimate |
Next milestones are company statements as recorded on each project page. Dates move; see the project page for the latest.
Which US projects are named in this guide?
Each mine page shows the project's stage, its latest study and its next milestone with the sources.
- Rare earth mines in the USEvery project, filterable by status
- Projects in developmentResource defined, feasibility or permitting under way
- Projects in explorationDrilling and sampling
- Halleck CreekA scoping study now, a PFS due Q3 2026
- Round TopA PEA now, a feasibility study due Q4 2026
- Elk CreekA 2026 feasibility study, financing pending
- Bear LodgeIn FAST-41 federal permitting
- Rare earth companies in the USWho is behind each project
- FAST-41 permittingFederal permitting timetables
- How to read resource estimatesTREO, grade and the three standards
Questions about rare earth project stages
What does PFS stand for in mining?
Pre-feasibility study. It is a comprehensive study of a range of options that fixes a preferred mining method or pit, an effective processing method and a plan to sell the product, with a financial analysis that can support probable reserves.
What is a DFS?
A definitive feasibility study, also called a bankable or full feasibility study. It adds detailed designs, costs and financial analysis, enough to support an investment decision or project financing. It has higher confidence than a pre-feasibility study.
What is the difference between a mineral resource and a reserve?
A resource is mineralization with reasonable prospects for economic extraction. A reserve is the economically mineable part of a measured or indicated resource, shown by a pre-feasibility or feasibility study. Inferred resources cannot be converted to reserves.
Does a feasibility study mean the mine will be built?
No. A feasibility study supports a decision but does not finance or permit the mine. Elk Creek, for example, has a 2026 feasibility study and major permits but needs project financing, and its construction start is a company target.
How long does it take to go from discovery to production?
US mines average about 19 years to begin operation (S&P Global, cited by OSTI), and the USGS places a new rare earth mine in its slowest class, seven years or more. Permitting alone has taken up to 17 years for US metal mines opened since 2000.
What does development mean on this site?
A project in development has a defined resource and feasibility, permitting or financing under way, but no commercial rare earth output. Round Top, Halleck Creek, Bear Lodge, Elk Creek and Brook Mine are in development.
Sources and verification
Each profile lists its sources, a confidence grade and a verification date. Order of authority: official records (SEC filings, agency documents), company documents and technical reports, research papers, then independent press. Syndicated copies and reference works are labeled and are never the only source for a number. Company-reported figures are labeled as such, and non-binding deals are labeled "letter of intent" or "conditional".
- USGS: The Principal Rare Earth Elements Deposits of the United States (Scientific Investigations Report 2010-5220) Official record
- eCFR: 17 CFR 229.1300, the S-K 1300 definitions for mining registrants Official record
- SEC: Modernization of Property Disclosures for Mining Registrants (Release 33-10570, Dec 2018) Official record
- JORC Code, 2012 Edition (JORC Committee) Independent press
- British Columbia Securities Commission: National Instrument 43-101, Standards of Disclosure for Mineral Projects (consolidation, Jul 25, 2023) Official record
- Canadian Securities Administrators: Staff Notice 43-307 on preliminary economic assessments (2012) Official record
- OSTI review, Minerals Engineering 249 (Kashyap et al., 2026) Research paper
- NioCorp 2026 technical report summary, exhibit 96.1 (SEC) Official record
- Ramaco 10-K for 2025 (SEC) Official record
Tags show what kind of source each link is. How sources are ranked
Guides
Which other guides are there?
Ten guides explain each step from mine to magnet, why the US is behind and how to read the technical reports behind each project in this directory.
- The chain Mine to magnet supply chain The five steps from ore to magnet, with every profiled US company at its step.
- The chain How rare earths are mined Open pits, underground mines, coal and mineral sands, and how ore becomes a concentrate.
- The chain How rare earths are separated Solvent extraction, RapidSX and chromatography, and the US plants that use each.
- The chain From oxide to metal and alloy Molten-salt electrolysis and metallothermic reduction, and who makes metal in the US.
- The chain How rare earth magnets are made Strip casting, pressing and sintering, and the US magnet plants with their stated capacity.
- The chain Rare earth recycling in the US Hydrogen processing, mechanical recovery and chemistry, and why volumes are still small.
- Why the US is behind Why the US cannot process rare earths Capacity against demand, and five obstacles with the evidence for each.
- Reading the reports Types of US rare earth deposits Carbonatite, granite, clay, coal and sands, with every US project mapped to a type.
- Reading the reports How to read resource estimates TREO, grade, JORC, NI 43-101 and S-K 1300, with a calculator and a worked example.
- Hub All rare earth guides The five steps from mine to magnet and a reading order for the ten guides.