This site was last updated May, 2011
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The best website on "Herkimer Diamonds"
The formation of these spheres of quartz are important evidence for understanding the history of Herkimer diamonds. I do not know of these forms of quartz occurring naturally anywhere else in the world.
Quartz Spheres - Unique and Important
A public service project always open to input from the community interested in Herkimer diamonds.
The specimen on the left is from the TCR location and part of the mine owner's collection (2009). It is about 1 cm across and shows most of the features that are common for these spheres. The spheres occur totally encased in hydrocarbon material and often contain one or more brilliant flat surfaces. This sphere also has a nice golden dolomite within it.
In the next two photos below you can see that these quartz spheres come in a variety of shapes, but never are they much larger than one cm in diameter. The photos each cover 2 cm across.
The flat surfaces on the spheres were puzzeling until I photographed the sphere below (7 mm top to bottom). Most of the spheres only show one to 4 of these flat surfaces but the sphere below shows many more. You can see that there are three flat surfaces on the top, three in the middle, and two of what should be three on the bottom. What we are probably looking is half of the six hexagonal faces of a quartz crystal. The other half would be on the back of this sphere, if they were developed, giving us 6 flat surfaces on top, 6 across the middle, and 6 around the bottom. (Photo DrD, 2009)
Below is the largest sphere found to date (2009) at about 10 mm across. (Photo DrD 2009)
There is another very circular feature found associated with Herkimer diamonds - circular impressions on the outside of crystals. Below you can see the faces and edges of a Herkimer diamond. On those faces are round impressions. The phenomenon that caused these is likely related to the same phenomenon that helped form the quartz spheres. At the arrow you can see the relationship between the faces of the crystal and the effects of the circular phenomena (Specimen from N. Adams Bob, from Fonda, NY (DA) loaned for photography 2009).
How is is possible to make these spheres and circular impressions? And what does it tell us about the history of Herkimer diamonds?
It is difficult to naturally make round spheres of clear quartz. Were these water worn, like pebbles on a beach? There seems to be no evidence to support that, especially when we can see very well formed flat features on the spheres that are smooth as glass. Did these form by some natural accretion process during the time when the sediments were being made - like the way a pearl is made? There is no evidence of layering in these spheres like one finds in a pearl. The most likely explanation is that these were formed inside nearly perfect spherical cavities. These spherical cavities were inside the black carbon material, hydrocarbon, and the quartz filled in those spherical cavities leaving behind spheres.
How can you make nearly perfectly spherical cavities inside the hydrocarbon? The best explanation is that at one time the material was viscous, slightly fluid, like thick syrup. It was likely oil. This oil contained gas bubbles and as the oil became hardened the bubbles were trapped, the hydrocarbon hardened and the bubble left behind a spherical cavity. The quartz then found its way along the porus layers in the rock (layers filled with holes) and into the spherical cavity contained within the solidified oil. The quartz then filled in the bubble cavity making the sphere. We then find the quartz spheres totally encased in carbon material and not anywhere else.
These quartz spheres are some of the best physical evidence within the Herkimer district that oil was present and influenced the history of how Herkimer diamonds were made. It is difficult to generate a more plausible theory, particularly given that gas deposits are found in the Finger Lakes region with similar wall rock alteration features. It is likely that there were several episodes of oil migration and several episodes of quartz events. It is also likely that the intensity/timing and flow direction of these oil events, in relation to the Herkimer diamonds, varies across the district (as do all the fluid migration events) resulting in variations within the deposits across the Herkimer district.
Not all the spheres were made of quartz
To the right is a sphere of calcite, formed in the same manner as described above.
It is likely that every Herkimer diamond mine has the potential to form these spheres. But there is probably a timimg relationship between the oil migration, the preservation of the spherical cavity and the availability of quartz solution. There are curved, and dome, features (see Odd Form Page) that might be found at every Herkimer diamond mine. Some of these are much larger than the spheres - up to several inches. But it is also likely because these curved features are either so small or so "ugly", and they are not in the shape of the typical Herkimer diamond, they would probably be discarded. If you have found these somewhere in the Herkimer mining district then please send us an email, or make a comment on the community page.
Please click and go to the FAQ page to read a brief description of a hypothesis for why clear crystals are so frequently found with hydrocarbon material.
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Web page author W. David Hoisington