. 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, the quartz within the vugs is interpreted to have formed during the
Carboniferous Period. Waxy organic material, silicon dioxide and
pyrite were 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 present in these crystals 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. == See also ==