Brockite - Anna Lee Mine, Custer County, Colorado, USA

(Ca,Th,Ce)PO₄ · H₂O

Brockite, a rare calcium-thorium phosphate mineral, is a noteworthy find from the Anna Lee Mine in Custer County, Colorado, a locality recognized for its unique pegmatite-hosted mineral assemblages. At this site, brockite typically forms as yellow to orange-brown granular masses or fine crystals, often in association with other secondary phosphate minerals. It is a product of the alteration of primary thorium-bearing minerals in phosphate-rich environments, reflecting the geochemical evolution of the pegmatite. Specimens from the Anna Lee Mine are sought after by collectors for their distinct coloration and their connection to the rare mineral assemblages of the area.

The Anna Lee Mine’s brockite is geologically significant due to its occurrence in thorium-enriched systems, which provide insights into the geochemical processes influencing rare-earth and radioactive mineral formation. As a rare mineral, brockite also highlights the diversity of phosphate minerals that can form in highly evolved pegmatites. The mine’s contributions to mineralogy extend beyond its scientific value, as brockite specimens are prized for their rarity and aesthetic qualities, cementing the Anna Lee Mine’s reputation as a key locality for rare phosphate minerals in Colorado.

Approx. specimen size: 22mm x 20mm x 12mm

Approx specimen activity on an SE International Ranger EXP: 10 000 cpm