This site was last updated on July, 2010
The best website on "Herkimer Diamonds"
After Herkimer diamonds, calcite crystals from the Herkimer diamond district are quite desirable. Here are photos showing the various forms that calcite takes when found within the Herkimer district. Preliminary research indicates that there are at least three calcite phases. But it has been very difficult to find specimens that show one calcite phase on top of another. Hopefully the community will help with this problem. Until we have more photos, clearer pictures, the ones posted here will act as examples. After quartz, calcite occurs in the most diverse variety of crystal shapes. Most of the shape variation is due to modification of the most common "nailhead" crystal form. The other modification is due to the crystal form changes that happen with the three different phases.
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Other Minerals - Calcite from Herkimer Diamond Mines
A public service project always open to input from the community interested in Herkimer diamonds.
The most common shape that calcite takes within the Herkimer district is what is called "nailhead" - the three pyramid faces (at the yellow arrow) are shaped like the head of an old hand forged nail. The following four photos attempt to show this common form. Many of the calcite crystals in the Herkimer district are modifications of this form and can be found in almost all the mines.
This grey translucent calcite is not common, but the crystal at the top showed well developed faces, which can be hard to find because most calcite in the district is etched. Think of the view as looking at the side of the "nail's head". I think, with a little imagination, the "head of a nail" can be seen. The specimen is from St. Johnsville (HBQ, donated 2008 by Mike Eggleston). The crystal at the top is 4.5 cm from tip-to-tip. Photo DrD. The next photo looks at the crystal from the side where the yellow arrow points showing the "nailhead" form.
As stated above, calcite is present throughout the Herkimer district and proably in many different shapes and colors. We need community support to get more calcite photos on this site. Send us a photo of your calcite specimen and help increase the knowledge about the unique mineral deposits.
In the above photo you can see that the crystal has the flat angled faces (yellow arrow again points at the top) and almost has a "rounded" shape, looking more like a "nail's head". When crystals of this form are also etched they look even more rounded (see the next photo). In the above photo, you can also see tan dolomite (which is iron stained 2nd phase white dolomite) and inclusions of needle suphides within the calcite. Photo, DrD. 2008
On the left, picture the "round" appearance of this calcite form, making it look more like a "nails head", is clearly seen. The rounded shape is the combination of crystal faces, as seen in the grey crystal above, along with etching that has smoothed out the face angles. The yellow and pink arrows are for reference to compare the faces on this crystal the above grey crystal. The "dark" center of the above calcite crystal is also due to clusters of needle sulfides. The crystal is 7.5 cm across. There is an elongated "Herkimer diamond" and a base of 2nd phase dolomite. The specimen is from St. Johnsville, NY (HBQ purchased 2008). Photo Dr. D.
The rhombic form of calcite is not that common, but along with the "nails head" form, it considered to represent the first calcite phase. These grey rhombs of calcite are on top of 3rd phase dolomite. The specimen below is from Palatine Bridge, NY. This photo (2 cm across) was donated by Brian Slater (NYSM) who did extensive research in a quarry there.
Some of the calcite from St. Johnsville (HBQ - purchased 2008) can be brilliant and a nice honey color. The specimen below is 8cm long and also shows 2nd phase white dolomite. Photo DrD.
The specimen to the left is from the NY State Museum, photo by Erik Rutnik. Donated from the Haldysz collection. Specimen is 9 cm across and the arrow points to the nails head termination. It is from St Johnsville (HBQ).
The honey, or amber, calcite can also be found as microscopic crystals in Fonda (DA). The two photos (below and right) are of specimens donated (by "Deputy Mike") in 2008. The specimens show 1.5 cm in each instance. This form of amber calcite has been found to occur as overgrowths on grey/white calcite - but such an occurence is extremely rare. This calcite is considered here to be second phase calcite. More research needs to be done on this, and more donation help.
Below the photo doesn't show the amber color as well, but it is an excellent example of the heavy calcite etching that occurs in Fonda (DA). The etched crystals are on the right side of the photo and the unetched are on the left, in a growth pattern similar to the photo to the right. Below you can see the small rhombs of the first phase dolomite (top center). Photos DrD.
There is also a photo of this honey/amber calcite coating Herkimer diamonds. Click here - >
Below is a photo of 3rd phase calcite. It occurs as a mounded coating, that is called "boytoyroidal". This specimen is from Middleville, NY (HDM - purchased 2008). The boytoyriodal calcite is over smokey druze and the specimen photo is 4 cm long. In the center of the photo you can see where the calcite is etched away showing hints of the quartz underneath. Again, heavy etching of calcite in the Herkimer district makes it hard to find these specimens preserved. What has been observed is druze where all that is left of this phase is a coating in crevices between the quartz - particularly in Middleville. Photo DrD., 2008
Web page author - W. David Hoisington, Ph.D.
Photos on the left and right are not attractive pictures, but represent what might be the most common form of calcite across the district, and can be found as small (.5 to 2 cm) crystals in vugs and many will be etched (as shown). On the left, the yellow arrows again points to the nailhead termination tip. In this specimen the crystal is "fat", stretched between the two yellow arrows. It is also showing only half of the nailhead faces. Specimen is 4 cm long, from Middleville, NY (AD) donated by Bill and Anne. Photo Dr. D., 2008
Specimen on the right is from Fonda, NY (DA). Black and yellow arrows point to the nailhead. Note the heavy etching. Specimen purchased 2010, 6 cm across, photo Dr. D.
To the right, the yellow arrows again points to the nailhead termination tip. In this specimen the crystal is stretched quite a bit between the two terminations resulting in a long prismatic shape (some cll them "barrel shaped"). This form appears to be rare for the district. Specimen is 4 cm top-to-bottom, from Middleville, NY (AD) donated by Bill and Anne. Photo Dr. D., 2008
Note: This crystal form is common in some MVT deposits
Occassionally (rare) the nails head form will be totally clear. The specimen below, donated by Bob (2008), is from St. Johnsville. Note also that the calcite is on a very unusual dark dolomite (a photo of this, with discussion, is on the dolomite page). Photo, DrD.
And a photo of white phase 2 calcite coating dolomite and coating calcite from HBQ. Click here - >
To the right is a photo of 3rd phase calcite collected at the TCR site (2009), with permission from the owner. Again, it occurs as a mounded coating called "boytoyroidal". This specimen photo is 2 cm across. The little bumby mounds are not only hard to find in the field, they are hard to find intact. Even these show significant effects from weathering. Photo DrD., 2010
Similar 3rd phase calcite has been seen at DA, but so severly etched it was not possibe to provide it as photographic evidence.
This form is unique to HBQ and yet also fairly common. There is a photo on the HBQ page.
Arrow points to first phase calcite under the second
It is not unusual for the naihead habit to occur in parallel growth as shown in the photo on the left. This specimen is from HBQ and Frank's collection. The line at the top is marcasite and there is white dolomite at the base. Photo by Frank, 2010.
The black arrow points to the tip of the nailhead like in the photos above.
