Where to Find Marcasite in Missouri

Missouri marcasite is the orthorhombic cousin of pyrite, found in the same Mississippi Valley dolomite host rocks. The Tri-State chat piles around Joplin in Jasper and Newton counties yield bladed marcasite rosettes and cockscomb aggregates, often pseudomorphing after pyrite. The Viburnum Trend mines (Buick, Brushy Creek, Sweetwater) produce blocky marcasite on dolomite with galena and sphalerite associations. The Old Lead Belt around Bonne Terre adds tabular and stalactitic marcasite. Surface marcasite oxidizes quickly to a sulfuric film and crumbles within months, so specimens should be coated with a thin lacquer if displayed in humid environments. The most productive ground is in Joplin chat field (Jasper County), Buick mine (Iron County), Old Lead Belt dumps (St. Francois County).

Casual hand collection of common rocks and minerals like marcasite is allowed on most BLM and U.S. Forest Service land in Missouri, with daily and annual limits set by the local field office. National parks, most state parks, and tribal land are off-limits. Always confirm rules before a trip.

Joplin chat field (Jasper County) is the standout. Other strong ground includes Buick mine (Iron County), Old Lead Belt dumps (St. Francois County). Marcasite has the same brassy color as pyrite but is paler and cleaves into bladed plates. A fresh fracture shows tabular outline; pyrite breaks conchoidal.