050219c

Limestone of the Knox Group, cross-section of a gastropod shell, mostly filled with lime mud (dark color like the surrounding matrix), remaining open space filled with calcite cement (clear and pink). Thin section, Kemper County Mississippi, approximately 3 miles below the surface.

033119

Dolomite (gray and white); this rock was once very porous, but all the pore space has been filled with calcite cement (stained pink with Alizarin red S), note partial replacement of rhombic dolomite crystals with calcite; dolostone of Knox Group, Mississippi, thin-section photomicrograph.

033019

Baroque dolomite growing into void within dolostone of the Knox Group, Mississippi, thin-section photomicrograph.

032919c

Ostracodes, some articulated and filled with calcite cement, in lines of the Knox Group, Mississippi. Thin-section photomicrograph.

Rock

Been tweeting these beauties for days. This one is pink calcite & zoned dolomite cement in a crack in Cambro-Ordovician Knox dolomite. 1/2 a billion years' non-stop fun.