This site was last updated on July, 2010
Definitions and Scope:

The best website on "Herkimer Diamonds"

This page will contain photos showing clear examples of one mineral growing over, or on top of, a different mineral.   Every attempt will be made to have photos that clearly show the relationship of one mineral phase to another.  This page is meant to serve as information to support the General Mineral Sequence diagram (click on minerals at the top of this page).  It is information to support the hypothesis that there were many fluid mineral crystallization events in the Herkimer diamond mining district.  It is proposed that the differences seen from one mine to another are largely due to changes in the effects of these fluid events at a given mine location.  Detailed mineral relationships for each individual Herkimer Diamond mine can be found on that mine's web page. 

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Minerals on Top of Each Other - Phase Relationships

A public service project always open to input  from the community interested in Herkimer diamonds.
Web page author W. David Hoisington

Dolomite and quartz are two of the most common minerals in the Herkimer diamond mine district.  This is a photo showing the second phase druze, prismatic form, growing over the edge of a dolomite crystal, probably rust stained second phase.  Specimen donated by Ted Smith of the Ace of Diamonds mine, Middleville, NY.  Photo Dr. D., 2008.  Close-up is below.

Although dolomite and quartz are the two most common minerals in the Herkimer Mining District, it is difficult to find specimens that show a crystalization relationship between the two.  In this specimen it appears as if the prismatic quartz grew after the dolomite.  But if you visit the quartz sphere page you will clearly see a dolomite crystal inside one of the spheres.


Below is a photo showing dolomite and two calcite phases.  The golden calcite is second phase and the white coating is third phase calcite.  Arrows with the numbers 2 and 3 point to the two phases.  The specimen is from AD, 2008, photo DrD.


The next photo is quite interesting.  At first appearances it looks like some strange form of dolomite.  But it is actually a form of phase two calcite on top opf dolomite, like in the above photo except clear.  It would be easy to pass by this, and probably toss it out while still in the mine.  From St. Johnsville, HBQ, donated by Bob.  Photo DrD, 2008 - 2 cm across the photo.
Relationship between quartz and dolomite - see the contact at the yellow arrow.
The most prevalent mineral phase depositional relationship in the herkimer diamond district is the relationship between the occurence of the druze phases and the Herkimer phase.  An excellent photo of this can be seen on the TCR page, and more photos can be seen on the druze page.
Calcite and dolomite also occur in several different episodes, although finding samples which contains multiple phases can be difficult.  An example is shown in the photos below.  More photos can be found on the calcite page and the dolomite page.
The next photo is also from St. Johnsville, HBQ, donated by Frank.  Photo DrD, 2010.  It supports the observation that there was a second white calcite phase at that location.  At the arrow on the right is a broken spot where you can see the golden calcite of phase 1, and clearly see the white calcite as a second coating.  The specimen is 8 cm tall.