This site was last updated on June, 2010
Quartz Crystal Habits within Herkimer Diamond Deposits
Definitions and Scope:
The best website on "Herkimer Diamonds"
Larger photos of the thumbnails presented on the main "Crystal Form" page. Included is identification information and the source link is embedded there (just click). In some cases additional information and comments are provided for each photo.
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Herkimer Diamonds on Matrix (host rock)
Circle of Diamonds ->
The specimen on the right specimen has not been cleaned (other than the the hydrocarbon debris that fell on the ground when the specimen was hammered out). You are looking at the bottom of a hydrocarbon pocket of Herkimer diamonds. It is slightly different than a clay pocket in appearance (see pocket photo page), but still most of the Herkimer diamonds are on the bottom. This is the "sister" picture to the "circle of diamonds" group specimen in with the crystal group photos. From Fonda, NY. (DA) Photo DrD.
Black Druze -->
New York State Museum Collection
Herkimer diamonds as small groups over druze is the fourth most common form of occurence (after singles in matrix - see above photo - and singles alone and then groups without matrix). This specimen is particularly unique in that clear/white crystals have formed on top of black "druze". Black druze with Herkimer diamonds is not common, and mostly restricted to the Herkimer Diamond Mine, and highly praised. The black druze is caused by inclusions and/or coatings of hydrocarbon.
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This is a fairly common form for Herkimer diamonds in matrix. Often one or two small crystals (the horizontal crystal is 1.5 cm point-to-point) are found in a cavity (vug) just big enough to hold them. There is no other quartz. The vug is lined with tiny dolomite crystals. These two crystals have a light rust coating, which is not common, but made the photo taking easier. The rock in which these are found is also very hard and can make a hammer ring and fragments fly. This is because it is "silica drenched", meaning a number of events happened that put some hard quartz into the rock. Wear eye protection! From Fonda, NY. (DA). Photo by DrD.
Most of the time Herkimers, when found on matrix, will have some other crystals associated with the matrix, like tiny dolomite druze (seen in the above photos). But often the pockets in Fonda that contain the very large crystals, nick named "goonies", are with a sandy matrix that is virtually barren. This specimen, on the left, is 7 cm across. Fonda, NY 1992. (DA) Photo DrD.
Black carbon pieces ->
<- Black carbon pieces
Herkimer diamonds as small groups over druze (photo on the left) is the third most common form of occurence (after singles in matrix - see above photo - and singles alone - see the singles page). This specimen is typical with a slight "dome" character to the matrix which has a pale smokey druze on it and then the Herkimers on top of that. It is not uncommon for the druze layer to break free and then serve as the base of the specimen. This specimen is 4 cm across and is from Fonda, NY, (DA)1982. Photo DrD. 2008
On the left, this is also a specimen of a "goonie", a large Herkimer diamond from Fonda NY (DA - 1992). The specimen also shows the smooth sandy character of the matrix. In addition this is a flattened crystal, or what is called a "tabular". This is an unusual specimen in that large tabular double terminated crystals in their original matrix (not restored) are difficult to find. The crystal stands 13 cm tall. Photo DrD., 2008
On the left, this is a "cleaned and restored" hydrocarbon pocket. it is just a piece of the foor showing a distribution of crystals. The larger Herkimer in the middle is 3 cm point-to-point. This pocket contained many more clear Herkimers than are shown here and the pocket was filled with black hydrocarbon. In addition there is no druze on the pocket wall, just very small, first phase, dolomite crystals. From Fonda, NY 1986 (DA). Photo, DrD.
Sometimes Herkimer diamonds can grow into tight places and still retain their natural form. In the specimen on the right there are fragments of the pocket wall rock with a double terminated Herkimer between. Most of the time these rock fragments are smooth. like in the photos above (and the one on the Diamond Acres site). This sample is rare in that some of the original wall rock crystals have escaped the severe erosion.
Upon close examination of the rock fragments they are coated with highly etched (eroded) dolomite crystals, but no druze. The top of the specimen is 8 cm across. From Fonda, NY (DA - 2003). Photo Dr. D., 2008
There are some very nice "vug" photos at the website given below. After you enter the site just scroll down to see the photos. These are the types of crystal finds that the average person might be lucky to find at one of the active mines.
Below: These Herkimer diamonds are on a totally different type of matrix - which is here termed "baby floater druze".
This specimen is from Fonda, NY (1982 - DA) and the larger crystal is 3.5 cm, bottom to top. In this photo you can see the "sparkle" of the druze which is actually a coating of tiny quartz crystals looking very much like Herkimer diamonds. This type of druze is very rare for this locale, but it is a druze that is found throughout the Herkimer Diamond mining district and is an important "clue" in understanding how Herkimer diamonds were formed. Photo, DrD., 2008
See also the "pocket pictures"
Web page author - W. David Hoisington, Ph.D.
To the right is the common type of matrix hosted (in the rock) Herkimer diamond as found in Middleville, NY (this one from AD). The cavity the crystal is in is called a "vug" and is different from a "pocket" (see the pocket pics). The vug is often lined with first phase dolomite that is coated with a film of hydrocarbon material. Photo, DrD. 2008.
There is also a photo showing this weathered matrix on the Diamond Acres mine site page.