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The Druze Page - The other quartz that can be found in the Herkimer mining district
Druze quartz is quartz that occurrs as coatings of crystals over rock (sometimes over other minerals). The crystals are usually touching each other, as can be seen in the photo on the left. It the Herkiner district there are several different phases of druze and each has its own character.
As with other mineral phases the druze episodes vary in intensity and effect across the district.
W. David Hoisington, Ph.D.
Black druze from HDM (2008)
Early Pyramidal Druze
Baby Floater Druze
To the left, is a specimen (6 cm across) with a coating of pyramidal white "normal" druze with some hydrocarbon on top. The pyramidal shape is like rows of little mountain peaks (which you can see in the photo below). This is from Fonda, NY (DA) and actually difficult to find there as most of the white druze is coated with a second smokey druze - some of which you can see on the right side. Most often the smokey druze will simply duplicate (as an overgrowth) the shape of the earlier white druze. Photo Dr.C., 2008. Below is a close up photo of the white early druze.
On the left is smoky druze and it is the most common form of druze in the district. This smoky color can range from a pale tint of color to the dark color in the specimen shown here. There is also a range in crystal size with most druze size looking like the above photo. The very dark smokey druze on the left is unusual for its size and color, and it has a "tinted" herkimer to go with it. The specimen is 5 cm across and is from Fonda, NY (DA - 2006). Photo DrC.
To the right is a close up photo of the flat black druze specimen shown above, but this is a side view. The importance of this picture is that it clearly shows the white "rind" that often underlies the primary black or smoky pyramidal druze. Sometimes it is well developed and laminations can be seen, much like tree rings. Other times it is poorly developed. This "rind" feature is not associated with the second phase prismatic druze (although some clay and disolution of minerals may be associated with the second phase) and it is not associated with the "baby floater" druze. See the discussion of this on the babyfloater druze page. Photo DrC, 2008.
To the left is black pyramidal druze from Middleville, NY (HDM). Specimen is 7 cm long. Black druze is not common for the entire Herkimer district, but more common from this location. Is is caused by hydrocarbon inclusions and coatings. This specimen was much blacker before it was cleaned due to a light carbon dusting that washed off. Photo DrC., 2008
Pyramidal Druze Variations
To the right is an example of both black druze and white druze. On close examination both the white and the black are of the same crystal formation and appear to have formed at the same time. The difference in "blackness" is due to the amount of hydrocarbon material available to the crystals during the time they formed. In addition, since some have a black dust as a coating (which does wash off) it appears that there was movement of hydrocarbon material in the pockets after the quartz druze was formed. This specimen is from Middleville, NY (HDM) and is 7 cm tall. Photo Dr.C. 2008.
It is clear in this sample that the hydrocarbon is not equally distributed to all the crystals (or all the solution which formed the crystals). This unequal mix of silica bearing fluids and hydrocarbon is seen throughout the district and is one of the main reasons for the differences between deposits.
Specimen from Turtle Clan Ridge showing "blue" druze - just a hint of blue Also an excellent example of saddle dolomite. Specimen is 5 cm across. Photo by Dr.C. 2009. The bluish color may be due to weathered chalcopyrite forming a bluish secondary copper mineral. Such bluish material has been seen at this location and at HBQ. The "rust" streaks also indicate that iron sulphides were likely present which usually accompany the copper.
To the right, the specimen is 9 cm across, from Turtle Clan Ridge (TCR), photo Dr.C. 2009. This is a first phase pyramidal druze. The difference is that the the crystals did not grow very much and they are coated with a thin layers of cryptocrystalline quartz (as seen in the above microsope photo). The result looks like a sparkling coating of snow. Since this is an early phase of mineral deposition it is often affected by all the events that follow (and there are many). Finding pristine samples of "snowball druze" is not easy, but it may be that altered samples are present in many locations if they can be recognized as such.
One can also ponder on the the shape of this unique druze and how it mirrors the shape of some rounded wall rock found within larger Herkimer diamond pockets. There is a photo on the baby floater page, from pocket wall rock in AD that shows this rounded texture. Why is this rounded texture so common in the Herkimer district?
In the above photo of the Ace druze there is second phase druze mixed in with a coating of "baby herkimers". This baby Herkimer coating forms a druze in most of the Herkimer mines throughout the district. This third druze phase is probably not officially a druze but it is often interwoven with the second prismatic phase and sometimes forms a coating all by itself. It is also important field evidence regarding the formation Herkimer diamonds. Because this phase of quartz mineralization is so important to the history of Herkimer diamond formation it deserves its own web page. Click -baby floater page.
How many other Herkimer deposit locations show this two layer druze association of both pyramidal and prismatic? And what does it look like?
Prismatic Druze Variations
This "Ace druze" is a mixture of small prismatic second phase druze and the third phase baby floater druze, often over a rust stained host rock. Specimen donated by the owner of the Ace of Diamonds mine. Photo Dr.C. 2009. The area around the blue arrow is exposed rock under the druze. You might note that there is no rind texture like there is with the first phase druze. The first phase druze is absent. The druze almost always has this dark golden brown appearance. In addition, on the edge of the plate can be found examples of the "picket fence" habit illustrated in the photo above. This druze apears to be quite plentiful at AD and can form large sheets (more than a foot square)
Note the small Herkimer diamond on the lower left (5 mm tip-to-tip).
"Needle Druze" - very rare
Two photos of what is here called "Ace Druze". The bottom is a close up of the one on the right. The druze occurs as rust brown plates generally less than an inch thick. They are fairly common for the Ace of Diamonds mine, and thus the name.
White layers probably resonsible for the "snowball" druze below. Note the thin layers flaking off of one small (1 mm) pyramidial quartz crystal in the center.
The photo left (specimen from TCR, 5mm across) shows how the prismatic druze will often grow in parallel groups, This specimen has not been cleaned. (Photo Dr.C., 2009) - showing the rust staining which is frequent at TCR. Dolomite crystals at the base.
This parallel growth pattern of the second phase druze is its characteristic, along with no rind contact with the host rock. This parallel growth is shown in the next series of photos.
The specimen below is also from Fonda. NY (DA - 1989). The specimen is 4 cm across and is a nice example of the association overlaping two druze events, one on top of the other, and then the Herkimer event last. Photo Dr.C..
The photo to the left shows a grey/smoky pyramidal (1st phase) quartz overlain by a prismatic needle druze. You can see a band of this druze at the top. Note the etching of the 1st phase quartz. The specimen is from TCR, and it is the only location in the Herkimer district where such a crystal habit has been found, and only one specimen was found. Photo Dr.C., 2010 - 3 cm across. Specimen collected with permisssion from the mine owners, 2009.
Close up of this specimen shown on the right.
The specimen on the right is from TCR and shows the parallel growth of the second phase druze quite nicely. Looks like a picket fence. Also visable is phase 1 druze, the rust covered little pyramids in the background. Distance across the photo is about 4 cm (Photo Dr.C., 2009). Phase 2 druze is well developed at TCR.
The specimen on the right is from DA and shows the parallel growth of the second phase druze on top of phase 1 druze, the white covered little pyramids at the base. Distance across the photo is about 2 cm (Photo Dr.C., 2008). Finding any examples of phase two druze at DA is difficult.
Phantom druze - closeup of the photo on the left. Photo, Dr.C. 2012.
The specimen above is 2 cm across. Purchased at the mine site (DA) in 2011. Photo, Dr. C. 2012.
Brown phantom druze from DA. This druze looks like smoky druze from a distance. Up close you can see brown phantoms inside the crystals. These phantoms are most likely due to the presence of brown hydrocarbon - an important piece of evidence for the oil and seed crystal theory. These are also found in the prismatic druze phase. Given the pulse nature of fluid movement in the Herkimer district it is likely that white phantom druze will be found.