Stromatolitic Jasper (Polished Slab)

Welcome to the website for EEEC’s 2600-pound polished slab of stromatolitic jasper.  The specimen comes from the Mary Ellen Mine of Biwabik, Minnesota.  It is a sample of the sea floor during a significant early period of geologic history, before there were complex forms of life on the planet, and when oxygen was still building up in the atmosphere from the microbes’  photosynthetic processes.

Donated By:

  • Made possible by gifts from Mark and Kandi Sutich (Biwabik Mary Ellen Stone Company) and the Geology Associates.

The Polishing Process

YouTube video of the Stromatolitic Jasper going through the polishing process. Video is sound free.

Watch the Polishing Process

Slab of jasper before it was polished.

The Before:

Before polishing, the rough-sawn slab of jasper did not look like much. The process of polishing involved hour and hours of sanding with a water coolant. The coarsest grits were used first, to remove surface imperfections and cutting marks. Then the slab was repeatedly sanded smooth, each with progressively polished slab; this is the natural shine of the rock once it is polished to a very flat surface with the finest grit.
A zoomed in photo of the stromatolites after the polishing process

The After:

The red-colored laminae are composed of jasper (microcrystalline quartz stained with hematite). the gray and silvery gray laminae are mostly magnetite (a magnetic iron oxide).