Geology of Pennsylvania

plateau region located in the eastern United States

Lansfordite is a mineral of magnesium carbonate (). It represents the pentahydrate of magnesium carbonate, and has the total formula . Landsfordite was discovered in 1888 in a coal mine in Lansford, Pennsylvania. It crystallizes in the monoclinic system (space group P21/c) and typically occurs as colorless to white prismatic crystals and stalactitic masses. It is a soft mineral, Mohs hardness of 2.5, with a low specific gravity of 1.7. It is transparent to translucent with refractive indices of 1.46 to 1.51. The mineral will effloresce at room temperature, producing nesquehonite.

Nesquehonite is a mineral of magnesium carbonate (). It represents the trihydrate of magnesium carbonate, and has the total formula . It was described in 1890 by F. A. Genth and S. L. Penfield and is named after its type locality of Nesquehoning, Pennsylvania, where it was sampled from a coal mine. Nesquehonite can form from the related pentahydrate Lansfordite by dehydration at room temperature.