BH250-100b

BH250-100b

Morton Gneiss Saprolite

The Morton Saprolite near Redwood Falls, Minnesota, formed through deep chemical weathering of the Precambrian Morton Gneiss, one of the oldest rock units on Earth. As the gneiss weathers, it produces a distinctive mineral assemblage including quartz, kaolinite, sericite (white mica), gibbsite, goethite, and hematite. Despite extensive mineralogical alteration, the saprolite preserves the original fabric and banding of the gneiss — a hallmark feature of saprolitic weathering. The weathered material is typically reddish to yellowish-brown, reflecting the abundance of iron oxides.

This saprolite has been the subject of multiple geochemistry student research projects, particularly focusing on its mineralogy, weathering processes, and geochemical evolution. Documentation and findings from these student studies are available through resources linked on this website.

Several student projects have explored this subject; please refer to the papers, abstracts, and posters available on the Geochemistry of Natural Waters website.

For more discussion on the Morton Saprolite see BH250-100

Bereket Haileab

From the rock collection of Bereket Haileab. Sample BH250-100b. Housed at Carleton College in Minnesota.

Thin section and hand sample