What are Herkimer diamonds?
The minerals of the Little Falls Dolostone are among the most famous in New York State. The Little Falls Dolostone is rock of late Cambrian age that formed at the bottom of a shallow sea about 495 million years ago. It crops out in the Mohawk Valley in Herkimer and Montgomery counties south of the Adirondacks. The material that would later form the beautiful crystallized minerals in this display case was probably deposited as quartz sand (SiO2), pyrite formed by bacteria and waxy, organic material. All of this material was encased in rock that was made up of two carbonate minerals, dolomite and calcite. As the Little Falls Dolostone was slowly buried by new sediments, the temperature slowly rose from 20 degrees C to 175 degrees C or slightly higher. The burial process took about 200 million years and reached a maximum depth of approximately 5 kilometers about 300 million years ago. Molecules of organic material helped to hold silica (SiO2) in solution. As the temperature rose, these or
