This site was last updated on June, 2010

History of the Herkimer Diamond  Host Rock

Definitions and Scope:

The best website on "Herkimer Diamonds"

The majority of the Herkimer Diamond deposits are found within a rock called the "Little Falls Formation".  This rock is here called the Herkimer host rock.  It is approximately 500 million years old.  If we can understand the conditions that existed when these rocks formed, and what happened to them over the course of history, then it can help us to understand how Herkimer Diamonds were formed.  On this webpage, special attention will be given to features that may be important to those conditions that helped form these unique crystal deposits. The video presentations below are artistic "approximations" of what the Earth might have looked like back through geologic time.  The information is presented for the general public.  For more detailed scientific studies please visit the scientific page ("science" link at the top of the page) and the new theory page (click on the link at the top of the page).
Giving Birth to the Herkimer Host Rock:
The World Before the Host Rock:
Preparing for the Birth of the Herkimer Host Rock:
Mountain Building, Faulting, and Fluid Flow:

Broad continental changes creating the setting for the making the Hermimer host rock

Changes in the world that happened just before the birth of the Herkimer host rock

This presentation shows a representation of multiple conditions during the time when the Herkimer host rocks were being made and the time just immediately following. An important feature is the presence of stromatolite layers - but they are only a part of the story.  Stromatolite layers, of this same age, occur all over the world.  Only in the Herkimer district do these layers contain the many different Herkimer diamond deposits.  What is important to consider are all the various geologic events that combined to shape the Hermiker host rocks. Along with unique "open" (framework)stromatolites, there were sand layers and erosion events. Later there was the formation of collapse breccias and other karst features (known througout the  world during this period in geologic history).  It is the combination of a unique set of events that gives us a very porous layers in a carbonate sequence, now called the Herkimer host rock.  It is a rock primed and ready for the growth of Herkimer diamonds.

There is some question about the nature of the porous layers.  There is little doubt that layers with high porousity existed, but exactly when did they develop the larger "pockets".  This is a question that will be explored in the next presentations - one on faulting and the one on glaciers.

This presentation (which is not available yet - more research needed) describes conditions after the host rocks were first formed that probably affected the formation of Herkimer diamond deposits.  There are basically two sets of events  that happened after the host rocks were burried to about 4000 feet.  First was faulting,  big cracks in the Earth along which large blocks of rock were shifted up (or down).  Second, there was fluid movement along these faults, and then out into porous (connected holes) layers in the rock.   It appears that  certain fault orientations were more conducive to fluid movement and certain layers in the rock more open to fluids moving through them. There is little doubt, based on field evidence and drill core samples, that these two events occurred within the Herkimer host rock (in specific areas).  A review of the "General Mineral Sequence" for the district suggests that there were many different fluid movement events linked to the formation of minerals in the Herkimer district.  What is still in hot debate is the timing of these faulting events and their exact relationship to the formation of Herkimer diamonds.  Thus far, a precise date for when the Herkimer diamonds were formed is not available.  Most researchers agree that it happened some time after the first faulting, and before the last of the faulting for the region. Thus there is often a link of the age of Herkimer diamonds to major continental collision events. 

Glaciers and Man:

The effects of glaciers and man on the appearence of Herkimer Diamond deposits was critical to having the Herkimer deposits become available to the public.  The glaciers removed hundreds of feet of rock exposing the Herkimer host rock to the surface and then man located the deposits and made them known to the public.  It is also imortant to note that the last geologic event to affect the Herkimer diamond deposits was erosion - water running through the rock and weathering both rock and crystals.   In some places there are large empty holes, or what might be called "mini-caves", in the Herkimer host rock.   In interviewing experienced collectors, many have recounted stories  of these empty holes. One mine owner said that there was one big enough to sit in,  Another collector spoke of one six feet long, and a couple of feet high, with only a single crystal tucked way in the back.  The recent weathering has also had an impact on the minerals - fractures in larger Herkimer diamonds, etching of dolomite and calcite, turning sulfides to rust, and moving around mud and small rock fragments. 

The presentations are in PDF format so they can be seen by any computer. The PDF files below were created using the Acrobat version released summer 2008.  It is an excellent program for presenting educational materials, but some visitors to this site have had difficulty viewing the presentation.  You will need Adobe Reader version 9.0, see the download link below (and some have had to repeat the download of both), but if that does not help you to view the presentation please contact Adobe.com (so they can help).  If you have trouble vieiwing the video and then find a solution, please email us and we will post it here.

Educational videos are used to help visitors with this information

The Herkimer host rocks are middle to upper Cambrian in age, or about 500 million years old and a little younger.  Some older literature (and diagrams) contain older dates.  Click on the web site below from Berkely for more scientific age information.
Above link is the clear presentation, but if you can't get it to work then click here -> ->
Above is the clear presentation, but if you can't get it to work then click here -> ->
A public service project always open to input  from the community interested in Herkimer diamonds.
A computer drawn simulation of what it might have looked like under water when upper Cambrian stromatolies were growing (same time as Herkimer host rocks) .  Painting by Dr. D.
Above is the clear presentation, but if you can't get it to work then click here -> ->
If you know how the rock was formed it can help you know where to look for Herkimer Diamonds

"Major events were the Taconian orogeny, caused by a collision with a volcanic island arc 460-440 m.y. (million years) ago; the Acadian orogeny, caused by a collision with a microcontinent called Avalon 410-380 m.y. ago; and the Alleghanian orogeny, caused by a collision with West Africa 330-250 m.y. ago."

Until science aquires a more accurate date, if you stated that Herkimer diamonds were somewhere between 300 to 450 million years old, you would probably be close to the current thinking of most scientists (as of the last update to this page).  Unfortuanately that is a 150 million year time spread - but it is the best that we have currently.
Web page author - W. David Hoisington, Ph.D.

It is obvious that several mineral fluid events moved through the Herkimer host rock.  Please click on the minerals tab at the top of the page to see the sequence.  What we do not know is exactly when these events happened.  Currently it is a process of gathering "clues" and piecing together the best fit explanation.

We also do not know the exact timing of the mineral events in relation to the various "mountain building" events.  More research is also needed here.

It is interesting to note that many of the larger pockets are much bigger than what is needed to hold the crystals that they contain, and that most (not including HBQ) show intense weathering of the "pocket" wall rock.  See the "mud and wall rock" link.
There is an hour long movie called "Prehistoric Disasters: Snowball Earth" which presents a picture of the Earth just before the Herkimer host rock was made.  It is a good presentation in that it can be easily understood by the general public but it also contains some scientific information.

Please note that there are also YouTube versions, but they are of lower quality