The ranking covers 82 companies and research institutes across the 284 records in scope, with the leading assignee holding 45 records. The top 5 assignees together account for 44.0% of all 284 records, and the top 10 account for 62.3%, so while filing is concentrated at the top there is still a long tail of entities with only one or two filings. This mix of a strong leader and a wide tail is typical of a field where core process claims are held by a few large mining and metallurgy specialists while smaller equipment and engineering firms file narrower circuit variants.

Carbon-in-leach (CIL) and carbon-in-pulp (CIP) are process routes where activated carbon is added directly to the cyanide leach slurry to adsorb dissolved gold, avoiding a separate leaching-then-adsorption step. It dominates because it is the commercial default for most modern gold plants, and the patent data reflects this: 94.4% of the 284 records in scope carry a C22B metal-extraction classification tied to leaching and recovery processes. Most recent innovation documented in this dataset refines this established route — oxygen addition, residence time control, cyanide consumption reduction — rather than replacing it outright.

Preg-robbing occurs when carbonaceous material naturally present in the ore adsorbs dissolved gold before it can reach the intended carbon or resin adsorbent, effectively stealing recovered value. It is one of the search terms defining this dataset's scope, and the most-cited records in the set — including US6482373B1 and its EPO counterpart EP0508542A2 — specifically address treating ore with recoverable metal values including arsenic-containing components, a common cause of refractory, preg-robbing behaviour. This makes pre-treatment of refractory ore one of the most heavily anchored claim areas in the field.

The dataset does not show a wholesale shift; C22B extraction claims still cover 94.4% of the 284 records and carbon-based routes remain the dominant documented technology. However, resin-based elution circuits appear as an active, more recent branch — the representative record WO2023283700A1, filed in 2023, describes a resin adsorption and dual-column elution circuit for separating gold and copper. This suggests resin-in-pulp is a growing niche within the broader field rather than a replacement for carbon-based adsorption at this point.

Based on IPC composition, the thinnest-claimed adjacent branches are electrolytic metal recovery (C25C, 3.9% of the 284 records), water and wastewater treatment tied to leach circuits (C02F, 3.5%), and soil or contaminated-land reclamation (B09C, 3.2%). All three sit far below the 94.4% claim density in core C22B extraction, and only 10 co-assignee pairs exist across the whole dataset, meaning collaborative filing in these adjacent areas is still rare. A first filer combining a defined leach-circuit output stream with one of these adjacent process steps would be working in genuinely thin prior art rather than contesting the anchored core claims.