Old structures used in the mining industry can be seen all throughout Joppenbergh mountain such as these Brick-Lined kilns. Kilns were used in the refining process of natural cement production. After the dolostone was mined, it was broken up into smaller pieces and then fed into the top of the kilns. The kilns fired the dolostone initially with wood but later coal in a process called calcination: the intense heat created drives off carbon dioxide (CO2 ) from the dolostone (CaMg(CO3)2) leaving behind a soft, more porous rock. The softer rock was then crushed into a fine powder by mills containing large grindstones made up of the local Shawangunk conglomerate. It was then placed into wooden barrels and shipped off via the Delaware and Hudson Canal and the Wallkill Valley railroad. Each barrel contained about 300lbs of the powdered natural cement product.
The top of the kilns were lowered in 2015 due to instability. The historic kilns were assessed, repaired, and lowered to preserve the history and maintain safety for the public.
Back to interactive map: https://wallkillvalleylt.org/joppenbergh-interactive-map/
Geology of the Hudson Valley: A Billion Years of History by Steven Schimmrich