The geologic history of these crystals began about 500 million years ago in a shallow sea which was receiving sediments from the ancient Adirondack Mountains to the north. The calcium and magnesium carbonate sediments accumulated and lithified to form the dolomite bedrock currently known as the Little Falls Formation and formerly as the Little Falls Dolostone. While buried, cavities were formed by acidic waters forming the vugs in which the quartz crystals formed. While the dolomite unit is Cambrian in age, the quartz within the vugs is interpreted to have formed during the Carboniferous Period. Waxy organic material, silicon dioxide and pyrite (iron sulfide) was present as minor constituents of rock made of dolomite and calcite. As sediment buried the rock and temperatures rose, crystals grew in the cavities very slowly, resulting in quartz crystals of exceptional clarity. Inclusions can be found in these crystals that provide clues to the origins of the Herkimer diamonds. Found within the inclusions are solids, liquids (salt water or petroleum), gases (most often carbon dioxide), two- and three-phase inclusions, and negative (uniaxial) crystals. A black hydrocarbon is the most common solid inclusion.