Weathering of Dolomite in Rosendale, New York

October 09, 2009


Photographer: Jordan Maendel
Summary Author: Jordan Maendel; Jim Foster; Stu Witmer

The photo above shows huge chunks of dolostone on a discarded railroad grade in Rosendale, New York. Rosendale is famous for the hardness of its natural cement made from dolomite. Natural cement is harder than the lime cement in use early in the nineteenth century, but was ultimately replaced by the faster drying Portland cement. The dolostone used to make natural cement was mined by hand over 100 years ago and the last mine closed in 1970. Now a number of abandoned mines are found nearby Rosendale. Weathering by freeze/thaw or frost heave and root wedging of the conifers above the mine entrance has disintegrated the rock. When water enters crevasses or joints within a rock and freezes, the ice expands to widen and deepen the joints over time as freeze/thaw cycles are repeated. Eventually, the rock breaks off into angular pieces.