Purpose: This study examines the emergence, character, and consequences of what it conceptualizes as “solid mineral barons,” powerful actors and networks that control capital, labor, protection, and market access around illicit mineral extraction and trade in Nigeria, and it evaluates how these dynamics differ across seven mineral-endowed states.

Methodology: The study adopts a qualitative documentary and comparative design, drawing on secondary evidence published between 2021 and 2026 from government agencies, international organizations, and peer-reviewed journals, and analyzing Zamfara, Katsina, Kaduna, Kogi, Sokoto, Plateau, and Benue States thematically across political economy, tactics, dark operations, and security-development consequences.

Results: The evidence shows that illicit mining functions as a shadow political economy rather than an isolated regulatory infraction, financing armed actors in Zamfara, generating territorial contestation in Kogi and Benue, compounding legacy environmental degradation in Plateau, and creating preventable exposure in Katsina, Kaduna, and Sokoto.

Conclusions: Effective intervention requires intelligence-led mineral governance, beneficial-ownership transparency, financial investigation, artisanal-mining formalization, and coordinated action among mining, security, environmental, and financial institutions rather than isolated site raids.

Limitations: The study relies on secondary documentary sources and does not include primary fieldwork or quantitative econometric testing.

Contributions: The study contributes an original analytical vocabulary, solid mineral barons and dark operations, and a structured seven-state comparative framework for mineral-security governance research in Nigeria and comparable resource-rich developing economies.