Glossary: terms used by the RareEarth Index, as the methodology defines them

Terms used across RareEarthIndex.com, defined as the methodology uses them. Section references are to the methodology (v2.1, October 10, 2026) unless stated.

The index

Level: The index value for a date, in USD, base 100 at the April 30, 2026 close. Computed from the weights and base prices of the rebalance period containing the date: level(d) = base_value × Σ w_i × P_i(d) / P_i,base, not by chaining daily returns (data page; §12.1).
Base value and base date: 100 at the April 30, 2026 close, the calculation date of the inaugural composition; inception (first published level) May 1, 2026. Each later rebalance or deletion period also has a base value: the level on its anchor close under the prior period, which keeps the series continuous (§8.4).
Provisional level: The newest published level. The daily run re-derives only that point once its inputs have settled, and appends new dates; every earlier level is final. Any wider change is a restatement and is disclosed in the reconstitution log (October 10, 2026 entry; data page).
Rebalance period: A span of dates sharing one set of weights and base prices, beginning at an anchor date: inception, a scheduled rebalance, or a corporate-action deletion. Four to date: April 30, June 18, August 19 and September 18, 2026 (inception.json).
Coverage gap: A date range with no published level, declared when a level cannot be computed from source data under the methodology in force; the index does not interpolate, carry forward or substitute a proxy. Disclosed on the chart, in the data file and in the log. None exists (§12.1).

Weighting

Free float: The shares of a company not held in strategic or restricted blocks: insiders and management, founders, government and sovereign holdings, cross-shareholdings, and any single shareholder above 5% disclosed as a strategic block are excluded. Free-float market capitalization is free-float shares times price, converted to USD (§5.2; constituent note §3.3). Aggregate free-float ratio at inception: 71.4%.
Modified market-capitalization weighting: Each constituent’s weight is its free-float market capitalization as a proportion of the aggregate, subject to a hard 10% cap on any single name; excess weight above the cap is redistributed pro rata across the uncapped constituents, iteratively, until no name exceeds the cap. No regional caps, sector caps or weight floors (§5.2).
Cap binding: A constituent is cap-bound when the 10% cap holds its weight below what it would otherwise be: because its own free-float weight exceeds 10% (Lynas, MP Materials), or because redistribution from larger names pushes it to the cap (JL Mag, USA Rare Earth, Neo Performance Materials). Marked ★ on the constituents page; the natural uncapped weights are disclosed there and in constituent note §6.
Rebalance versus reconstitution: A rebalance resets weights to current free-float market capitalizations, subject to the cap, with free-float share counts held constant; it adds or removes no constituent except for a corporate action. Quarterly, on the third Friday of March, June, September and December, or the prior US trading day if that is a US market holiday (§8.1). A reconstitution re-applies the full eligibility framework to the candidate universe, removes companies that no longer qualify, adds new ones, and refreshes free-float share counts. Semiannual, June and December, same calendar slot (§8.2).
Corporate-action deletion: Removal of a constituent between scheduled events after a takeover resulting in delisting, a suspension beyond ten consecutive trading days, insolvency, a qualifying spin-off, or a change of business that fails the activity screen (§8.3). Applied at the last traded close, with the weight redistributed pro rata at drifted weights, no cap re-applied, and no replacement until the next reconstitution (§8.4). One to date: Australian Strategic Materials, August 19, 2026.

Eligibility

ADTV: Average daily traded value: closing price times volume, converted to USD, averaged over the trailing 90 trading days. The liquidity floor is USD 500,000, or USD 1,000,000 for TSXV listings, which carry a higher bar to compensate for the venue’s lower baseline liquidity (§4.3).
Market-cap floor: USD 50 million, measured as the 30-day average of daily closing market capitalization in USD-equivalent terms (§4.3). A company within 10% of either floor is eligible if it clears the floor and ineligible if it does not; the index does not round in either direction (§10.3).
JORC: The Australasian Joint Ore Reserves Committee code, the reporting standard for exploration results, mineral resources and ore reserves used by ASX-listed companies. An advanced-stage explorer is eligible only with a published JORC- or NI 43-101-compliant rare earth resource where the project is the company’s primary asset (§4.1, §9). Under v2.0 an Inferred resource is sufficient (constituent note §8.6).
NI 43-101: Canadian National Instrument 43-101, the disclosure standard for mineral projects used by TSX- and TSXV-listed companies; the Canadian counterpart of JORC for the purposes of §4.1 and §9.
Activity screen: The first of six screens: a company must derive the majority of its enterprise value from rare earth extraction, processing or separation, magnet or alloy manufacturing, recycling, or advanced-stage exploration (§4.1). Applied as written to companies in transition: eligible when the activity is primary, not before (§10.1).

Rare earths

Rare earth elements (REE): The seventeen metallic elements of the lanthanide series plus scandium and yttrium. Most are not geologically scarce; what is scarce is economically viable concentration together with the processing infrastructure to separate them (§1). All seventeen are within scope of the activity screen (§7).
NdPr: Neodymium and praseodymium, the two rare earths that make NdFeB permanent magnets used in electric-vehicle motors and wind-turbine generators, usually produced and priced together as NdPr oxide. The product line of Lynas, MP Materials and the Arafura, Lindian and Pensana projects (§7; constituent profiles).
LREE and HREE: Light and heavy rare earth elements. The profiles use LREE for the lighter lanthanides (lanthanum, cerium, praseodymium, neodymium, samarium, as in MP Materials’ bastnasite ore) and HREE for the heavier ones with yttrium (dysprosium, terbium, yttrium, holmium, erbium, as at Critical Metals’ Tanbreez). Dysprosium and terbium are the heavy elements needed for high-temperature magnets (§7).
TREO: Total rare earth oxides: the combined rare earth content of ore or concentrate expressed as oxide, the grade figure quoted in resource statements (for example 4.06% TREO at St George Mining’s Araxá project, constituent note §5.5).
Ionic adsorption clay: A deposit type in which rare earths are adsorbed onto clay minerals rather than locked in hard-rock minerals, typically with a heavier element basket (yttrium, dysprosium, terbium). The deposit type of Aclara’s Penco Module and Carina projects and Meteoric’s Caldeira project (constituent profiles; §4.1).
NdFeB: Neodymium-iron-boron, the rare earth permanent magnet alloy. Manufacturing NdFeB magnets or REE-bearing alloys as a primary product line is an eligible activity (§4.1); the inaugural construction applied the screen to rare-earth-bearing magnet and alloy revenue only, excluding ferrite magnets (constituent note §8.4).