CHARACTERIZING THE CHEMISTRY OF ROSENDALE NATURAL CEMENT TO AID IN THE IDENTIFICATION OF SIMILAR DEPOSITS IN THE NORTHERN AND CENTRAL APPALACHIANS

Published data on the geochemistry of units historically used in the production of North American natural cement are sparse. As part of an effort to characterize units suitable for manufacturing natural cement, we used a portable XRF to conduct a preliminary geochemical analysis of samples collected from the late Silurian Rondout Formation near Rosendale in the Hudson Valley of New York. Historically, dolostone selectively extracted from the Rondout Fm was blended by producers using proprietary ratios to produce the finest quality natural cement historically available.

The Rondout Fm comprises the Rosendale, Glasco, and Whiteport Members. While historical accounts suggest that the sandy Whiteport Mbr was more valuable than the clayey Rosendale Member, our results suggest that a 2:1 ratio of material from the Rosendale and Whiteport Mbrs was used in natural cement production. Anecdotal historical accounts also suggest that the Glasco Mbr, a fossiliferous dolomitic limestone, was avoided during mining because of its relatively high quartz content. Similarly, our analysis suggests that the quartz wacke of the Binnewater Fm and the interbedded red shale and limestone of the High Falls Fm that unconformably underlie the Rondout Fm are also not suitable for cement production.

During the nineteenth and earliest twentieth centuries, Rosendale natural cement was utilized extensively in the construction of canals, bridges, military fortifications, and significant historical landmarks. Contemporary standards and guidelines for the archeological and historic preservation of landmarks often require the use of original materials and techniques when making repairs and improvements to protected structures. These mandates are leading to a resurgence of interest in natural cement production, particularly in Pennsylvania, where geochemically similar deposits may exist in the Cambrian, Ordovician, and Silurian sections. Unfortunately, few historical records associated with the natural cement industry survive. The last producer of natural cement in the Rosendale area was the Century Cement Company, whose archives are preserved by the Century House Historical Society. These archives contain some quality control documents associated with cement chemistry, but analyses utilizing modern techniques are badly needed.