Cyanide Free Gold Processing Patents: Leaders & White Space 2026
- Filing has gone quiet since the 2021 peak. The dataset shows a -100% swing from 2021 (13 records) to 2024 (0), the last year publication lag lets us treat as complete — a sign the field's early claim space is settling, not that interest has stopped.
- One family of thiosulfate patents anchors the whole citation graph. Three related US filings on thiosulfate leaching of precious metals sit at the top of the citation table, each cited 20 times or more — durable prior art that any new thiosulfate claim has to search around.
- The leader (29 records) sits well ahead of a long tail. Eleven companies make up the entire ranked list, with fifth place at 7 records and tenth place at just 1 — a concentrated head and a thin tail of single- or few-filing entrants.
Filing growth compares 2021 (13 records) with 2024 (0) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field.
A narrow chemistry, a small but active filer base
Cyanide-free gold processing covers a handful of alternative leaching chemistries — thiosulfate leaching, glycine leaching, and related resin-adsorption and detoxification steps — positioned as replacements for cyanidation. The 101 records in scope span 2015 through the first half of 2026, concentrated overwhelmingly in metal extraction and refining (IPC C22B), with meaningful secondary activity in separation processes and compounds of other metals. This is a metallurgical-process field, not a materials-science one: claims tend to sit on reagent formulation, catalysis (notably copper-assisted thiosulfate systems), and the recovery/regeneration loop rather than on novel compounds.
Filing rose to a peak of 13 records in 2020, held near that level into 2021, then fell away sharply. Because publication trails filing by roughly eighteen months, the 2025-2026 figures are still filling in and should not be read as a slowdown in real R&D activity — but the complete run through 2024 already shows the steep drop the hero card reports.
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Filing trend and technology composition
Two views of the same 101-record set: how filing has moved year over year, and which IPC subclasses carry the claims.
Filing trend, 2017-2026
Records climbed from 9 in 2017 to a peak of 13 in 2020, sustained through 2021, then declined to 0 by 2024 — the complete run the -100% figure is drawn from. 2025 and 2026 are omitted from any growth reading because publication lag means they are still incomplete.
IPC subclass composition
C22B (metal extraction & refining) appears in 98.0% of the 101 records, confirming this is fundamentally an extraction-chemistry field. B01D (separation processes) at 34.7% and C01G (compounds of other metals) at 30.7% point to solid-liquid separation and precipitate/compound recovery as the two biggest secondary claim areas. Catalysis-specific filings under B01J sit at 11.9%, and electrolytic recovery (C25C), wastewater treatment (C02F) and organic-chemistry classes (C07C, C07D) each account for 2-3% — small but present adjacent branches.
Shares are the percentage of the 101 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Cyanide Free Gold Processing with Eureka
This page is one run against one query. Ask Eureka your own question about cyanide free gold processing and every answer comes back with the patent numbers behind it.
Try EurekaThe claims other filings cite
Method for carbon-catalysed thiosulfate leaching of gold-bearing materials
The present disclosure is directed to a gold recovery process in which activated carbon or another carbon-based material is used to accelerate thiosulfate leaching of gold from a gold-bearing material.Filed by Barrick Mining Corporation, published 2020-07-23 as US20200232065A1.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US20040115108A1 | Method for thiosulfate leaching of precious metal-containing materials | 33 |
| 2 | US20090056500A1 | Resin-in-leach process to recover nickel and/or cobalt in ore leaching pulps | 28 |
| 3 | US7544232B2 | Method for thiosulfate leaching of precious metal-containing materials | 28 |
| 4 | WO2016168933A1 | Methods for selective leaching and extraction of precious metals in organic solvents | 25 |
| 5 | US7722840B2 | Method for thiosulfate leaching of precious metal-containing materials | 20 |
| 6 | US20070089566A1 | Method for thiosulfate leaching of precious metal-containing materials | 17 |
| 7 | US20180112289A1 | Methods for selective leaching and extraction of precious metals in organic solvents | 16 |
| 8 | US8821613B2 | Method for thiosulfate leaching of precious metal-containing materials | 14 |
| 9 | US8097227B2 | Method for thiosulfate leaching of precious metal-containing materials | 10 |
| 10 | US20040237721A1 | Anoxic leaching of precious metals with thiosulfate and precious metal oxidants | 10 |
Citation counts inside a searched corpus favour older filings by construction — treat this as a map of influence on later drafting, not a ranking of current commercial importance.
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Three read-throughs from the trend, the citation table and the class breakdown that matter more than the raw counts.
Thiosulfate leaching prior art is dense and durable
Three related US filings on thiosulfate leaching of precious metal-containing materials each carry 20+ citations, with the oldest at 33. Any new thiosulfate reagent-stability or dissolution-rate claim has to be drafted around this cluster, not just around the newest filings.
The claim rush has cooled, on the complete years
Filing fell from a sustained peak of 13 records in 2020-2021 to zero in 2024, the last year unaffected by publication lag. That is a real contraction in new claim activity, not an artefact of recent-year undercounting.
Separation and compound-recovery steps are the real secondary battleground
Nearly every record touches core extraction (C22B), but over a third also claim separation processes and nearly a third claim compound-of-other-metals recovery — these secondary steps, not the base leaching chemistry, are where differentiated claims are still being drafted.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to cyanide free gold processing, with the prior art for and against each one.
A concentrated leader, a thin tail, little co-filing
Eleven companies make up the entire ranked list this dataset returns. The leader holds 29 records against a fifth-place figure of 7 and a tenth-place figure of just 1 — a steep drop-off rather than a gradual one. Co-assignee activity is minimal: only five pairs appear at all, none stronger than two shared records, suggesting most of this work is filed solo rather than through joint ventures or research partnerships.
One filer well ahead of the field
The leading assignee's 29 records sit far above the rest of the ranked list, reflecting sustained multi-year investment in thiosulfate-route IP rather than a single large filing event.
A short, steep tail below the leader
From fifth place (7 records) to tenth place (1 record), the ranking narrows quickly. Most of the eleven ranked companies hold only a handful of filings each, consistent with a technical niche rather than a mainstream extraction category.
Little joint filing across organisations
Only five co-assignee pairs appear in the dataset, each with at most two shared records, and several of the strongest pairs are individual inventors rather than corporate partnerships. IP in this space looks largely internally developed.
| Assignee | Recent year | YoY |
|---|---|---|
| PLACER DOME TECHN SERVICES | 0 | — |
| Barrick Gold Corporation | 0 | — |
| EXCIR WORKS CORP | 0 | — |
| Vale Inco | 0 | — |
| University of Saskatchewan | 0 | — |
| PIVAZYAN ARMAN | 0 | — |
| MONTANA TECH OF THE UNIVERSITY OF MONTANA | 0 | — |
| FUJIFILM Holdings Corporation | 0 | — |
Where to look next
The dataset points to a settled core and a few branches still open for a differentiated first claim.
Map the thiosulfate citation cluster before drafting
The top five cited records, all thiosulfate-leaching filings from the same family lineage, define the prior-art boundary for reagent-stability and dissolution-rate claims. A freedom-to-operate review should start there, not with a general keyword search.
Explore citation mapping in EurekaWatch the under-claimed secondary steps
Effluent detoxification, reagent regeneration and resin-in-leach recovery each show up in the IPC mix at low double digits or below, well under the core extraction share — these are the branches most likely to support a defensible new claim.
Run a white-space search in EurekaCommon questions on cyanide-free gold processing patents
The dataset is dominated by thiosulfate leaching, often catalysed with copper or carbon, alongside glycine leaching as a secondary chemistry. Supporting process steps — resin adsorption to recover dissolved gold, effluent detoxification, and reagent regeneration — appear as claim elements around the core leaching step rather than as standalone technologies. Metal extraction and refining (IPC C22B) appears in 98.0% of the 101 records in scope, confirming this is treated as an extraction-chemistry problem first.
The most-cited records in this dataset are a cluster of related US filings on thiosulfate leaching of precious metal-containing materials, each cited 20 or more times, with the oldest at 33 citations. In terms of filing volume, the ranking is led by one company with 29 records against a field of eleven ranked companies total, with a steep drop to single-digit counts by fifth place. High citation counts reflect influence on later drafting more than current commercial dominance, since citation counts favour older filings.
On the years complete enough to trust, activity is shrinking: filings fell from a sustained peak of 13 records in 2020-2021 to zero in 2024, a -100% change over that span. Because publication lags filing by roughly eighteen months, 2025 and 2026 figures are still filling in and should not be read as evidence of a further decline. The honest read is that the initial wave of claim activity around 2020-2021 has passed, and it is too early to say what comes next.
This 2020 filing from Barrick Mining Corporation describes using activated carbon or another carbon-based material to accelerate thiosulfate leaching of gold from gold-bearing material. It sits within the same thiosulfate-leaching cluster that dominates the most-cited records in this dataset, so anyone drafting a carbon- or copper-catalysed thiosulfate claim should check its specific claim scope directly rather than assume it is clear.
The IPC composition shows core extraction claims (C22B) are heavily filed, but adjacent branches are thinner: electrolytic recovery (C25C) and wastewater treatment (C02F) each sit at only 2-3% of the 101 records, and catalysis-specific filings (B01J) at 11.9%. Reagent regeneration loops, effluent detoxification, and resin-in-leach recovery from pulps show up as elements within broader filings rather than as the focus of dedicated, heavily-claimed patents, which is where a first, narrowly-drafted claim is more likely to clear prior art.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.