Mindat Logo

Twenty Years of Collecting at the Buckwheat Mine Dump: My Personal Observations

Last Updated: 1st May 2011

Twenty Years of Collecting on the Buckwheat Mine Dump: My Personal Observations

Bruce T. Mitchell

The minerals of Franklin and Sterling Hill, New Jersey, have come to have an almost legendary status among mineral collectors. The area, of course, is known primarily for the fluorescent minerals that were found in the zinc mines there, and spectacular combinations of fluorescent red calcite, green willemite, lemon-yellow esperite, purple hardystonite, and other even rarer minerals command high prices today. The mines have long since closed, but the opportunity to collect the minerals is still available at both the Franklin and Sterling Hill* sites, thanks to the dedication of collectors of fluorescent minerals and the societies that they belong to who have worked to keep these areas open. Many collectors of Franklin material tend to look down upon the lowly Buckwheat Dump, thinking that the good material that once might have been found there is long gone, and what remains is clearly not worth the effort to collect. And it is quite true that the casual collector is unlikely to find one of the magnificent three- or four-color combination pieces there that Franklin is famous for. But for those who love to get out and collect minerals just for the joy of finding something (instead of buying it), or for those who are looking for the really unusual mineral combinations, the dump is absolutely worth the time. In this article, I will attempt to summarize my own collecting experience for the benefit of those who might wish to try for themselves.

I have been systematically collecting minerals on the Buckwheat Dump for the past twenty years. By “systematically”, I mean making trips to the dump when I knew what I was looking for, with the benefit of a degree in geology and a portable ultraviolet light to identify the minerals that I found. As a youngster in the 1970’s I went to Franklin several times with my father, visiting both the Buckwheat and Trotter sites, but my method at the time was simply to pick up anything that looked interesting and check it out when I got home. While I found some attractive calcite/willemite specimens using the “blind pick-up” method, I would certainly recommend a more informed approach for those who might go now. For those who plan a trip to Franklin, a few suggestions from my own experience:

• Absolutely, buy and bring a portable ultraviolet light. You will more than likely be collecting in the daytime and will need to screen through a lot of material to find the one or two real gems that are worth adding to one’s collection. There is a small shed at the back of the dump, dark inside when the door is closed, where one can view one’s finds under the ultraviolet light.
• Learn what the fluorescent material looks like in ordinary daylight and, in general, learn all you can about the Franklin minerals ahead of time. This can be done by looking at some of the material in the museum or in other peoples’ collections, but also by reading and visiting the websites that feature the fluorescent material from Franklin. You will also find that the museum staff will be much more helpful if they realize that you have some basic knowledge, at least, and are not simply one of the tourists expecting to find gold or gems on the dump.
• There are many collectors living in the Eastern U.S. who have far more experience collecting on the Buckwheat Dump than I do. Living in Texas, my trips have been generally limited to annual events. At the museum, there are usually experts in the mineralogy of the Franklin area who can help. It should also be noted that once a year, the Franklin-Sterling Hill Gem and Mineral show is held (late September) and if you have the good fortune to attend you will learn far more from the many expert collectors who are there.
• I have included a couple of links to sites that I have found helpful in identifying material from the Buckwheat Dump. In the case of Mindat site in particular, be aware that the specific description of the Buckwheat Pit (Buckwheat Mine) is not quite the same thing as the Buckwheat Dump; the dump has material from several different sources (as I understand it) and not all of the minerals that can be found on the dump are listed in this reference.

o http://www.njminerals.org/index.html
o http://www.njminerals.org/oremicro.html
o http://www.njmineral.com/collectingtrips/buckwheatdump.html
o http://www.mindat.org/loc-6833.html
o http://franklinmineralmuseum.com/index.htm


The following section lists the fluorescent minerals that I have found on the Buckwheat Dump. I should say at the outset that I have not positively identified any of my specimens with x-ray diffraction or similar techniques. Rather, I have narrowed the possibilities from the color of the fluorescence and associations, and then run chemical and analytical test (hardness, cleavage) the “old-fashioned” way to make a final I.D. In many cases (calcite, willemite, etc.) there is no question in my mind that the mineral is positively identified: a moderately hard, glassy-green mineral with a brilliant green fluorescence associated with franklinite and calcite might possibly be something other than willemite but I can’t imagine what. For these, next to the mineral name, I have included in parentheses the label (CERTAIN). Other minerals, like fluorapatite, fit the specific description for their type of fluorescence and mineral associations and their presence on the dump has been reported by many other collectors, but I haven’t necessarily tested them. These would have the label (PROBABLE). And then there are several minerals that appear to fit the description and physical characteristics that I’ve read about but seem to me to have considerable doubt in their identification, and these I have labeled as (POSSIBLE).

Calcite (CERTAIN): Calcite, fluorescing under a shortwave ultraviolet light (SW) in shades of color ranging from flaming orange-red to soft pink, is by far the most abundant mineral that can be found on the Buckwheat Dump. The daylight color ranges from nearly white to dark gray, and tinted with various light colors. As a very general rule, the more dark-gray calcite does not fluoresce as brightly as the lighter colored material, but some of the calcite has little or no fluorescence regardless of the daylight color. The response of calcite under longwave ultraviolet light (LW) is generally much less intense, but some of the lighter material will fluoresce fairly brightly at times with an attractive pinkish-orange color. In addition to the common white to gray material, the so-called “salmon calcite” is a popular find. This is calcite which, under daylight, has a good pinkish orange to bright orange-red color resembling fresh (uncooked) salmon. Salmon calcite has a fairly good reddish-orange fluorescence, SW, but typically not as intense as the best white or light gray material.

A more uncommon and much more interesting calcite that can be found on the Buckwheat Dump is the two-color fluorescent calcite described by Manuel Robbins (1983). This calcite fluoresces with the typical orange-red under SW, but under LW there are patches of bright blue-white or violet-white fluorescence. Upon closer inspection under SW, again, one then observes that the fluorescent color is bright pinkish-orange, or almost a hot pink, in the places that coincide with the patches of LW fluorescence. Finding this calcite will be difficult, since there is so much calcite of every shade of white, tan, and gray lying on the dumps already. The two-color calcite that I found was white in color and with a very coarse cleavage, and had associated with it irregular “blebs” of reddish-brown willemite that fluoresced green under SW. The picture below shows a piece of this interesting calcite, under SW on the left with the pinkish patches of fluorescence amidst the usual orange red color, and with the green the of willemite, and then under LW where the bright violet-white fluorescence of the calcite is dominant:


Two-Color Calcite (pink, orange-red) with Willemite (green), SW

Two-Color Calcite (violet-white), LW


Diopside (PROBABLE): Small grains of diopside, with a bright blue-white fluorescence SW can be found in white, crystalline masses of the Franklin Marble, associated with possible tremolite (fl cream-white SW) and phlogopite mica (fl gold SW). I have found some of this material on the dump. Experienced collectors have told me that the bright blue-white specs are the diopside, and the less bright grains with the cream-white fluorescence are tremolite but without an actual XRD one cannot be completely certain.

Dolomite (POSSIBLE): Dolomite definitely occurs on the Buckwheat Dump in considerable quantity, but it is usually non-fluorescent. The dolomite that fluoresces is often associated with calcite and has a medium- to dull-red fluorescence SW (“crazy” calcite). I have also found two interesting specimens with a core of a very light gray carbonate, surrounded by a brown carbonate with franklinite and then a fair amount of the usual calcite/franklinite. The calcite has the typical bright orange-red fluorescence, but the light gray carbonate has a more modest pinkish-red fluorescence SW that looks quite different from the calcite. It is clearly a carbonate of some sort, for it effervesces in hydrochloric acid, but it is harder than calcite with more of a pearly luster, and a less prominent cleavage. My best guess is that this material is dolomite, but it is also possible that it is something else with enough included calcite to fluoresce.

Esperite (PROBABLE): Yes! I have found esperite on the Buckwheat Dump, associated with willemite, franklinite, calcite, and minor amounts of hardystonite. The esperite was present in a few small grains and patches on the piece, but there was no mistaking the lemon-yellow SW fluorescence. It is my understanding in talking to other collectors that other folks have found esperite on rare occasions also, but typically only as small pieces or pieces with just a few spots of the mineral. The beautiful showy pieces of esperite/willemite/calcite that fluorescent collectors dream about came out of the Franklin Mine later and did not end up on the Buckwheat Dump.

Fluorapatite (PROBABLE): For the purposes of this article I will include all variants on the apatite group of minerals under this heading, recognizing that rare species like turneaurite or johnbaumite can be found on the dump as well as fluorapatite itself. In some cases, it may not be possible to distinguish the different sub-species without testing. The fluorapatite that I have found on the dump always has an orange to burnt-orange fluorescence under SW, ranging in intensity from fairly bright to rather dull, and with no fluorescence LW. I have found it most commonly in a dark and fairly heavy fine-grained matrix rock associated with fluorite, disseminated grains of fluorescent willemite, and sometimes sphalerite. Mr. John Cianciulli, who looked over my finds one day, confirmed that he thought that it was fluorapatite. On one occasion I found some fairly bright material associated with willemite in a matrix of massive andradite and hendricksite, and another time associated with fluorescent calcite and willemite. Possibly the brighter material associated with willemite and hendricksite would have been considered “svabite” to the old-time collectors since it occurs with ore material, but I have not tested it for arsenic content. A piece of this material is pictured here, and the reader can make his own guesses:


Fluorapatite (orange) with willemite (green), andradite, and hendricksite, SW


Fluorite (CERTAIN): Fluorite is not uncommon on the dump, usually occurring in a dark-grained matrix rock that appears to have a lot of franklinite in it, with fluorescent willemite, sphalerite, and sometimes fluorapatite as associates. This fluorite is commonly pinkish to red-brown in color and fluoresces with an attractive soft blue-green or teal color (SW or LW). When it is associated with willemite, fluorescing bright green, it is quite easy to see the color difference. This fluorite also has a pronounced phosphorescence, and thermoluminescence: when a small piece is heated it glows with a bright blue-green color. Other fluorite can be found that fluoresces with a more typical blue to blue-violet fluorescence that is best LW. The red-brown fluorite with the blue-green fluorescence is often referred to as chlorophane in older literature. It is light-sensitive, and when exposed to bright sunlight or incandescent light it will quickly lose its ability to fluoresce. The best specimens are generally found by splitting open a larger stone to reveal a fresh, unexposed surface and knowledgeable collectors then promptly wrap up the material and keep it stored in the dark. Here is a good photo of some of this fluorite from the Buckwheat Dump:


Fluorite (blue-green) with willemite (green), SW


Hardystonite (PROBABLE): I have found hardystonite, fluorescing with a purple color under SW ultraviolet, on several occasions at the Buckwheat Dump. It is definitely not common and will require some diligent searching and luck. Much of the hardystonite that I have found is in rather small, isolated grains in fluorescent calcite, with willemite and franklinite. In this association the fluorescence is unmistakably purple but is not as bright as the better-quality massive material that came directly out of the mine (i.e. the Parker Shaft material). I have also found one or two pieces of more massive hardystonite associated with willemite and andradite and this has the more typical vivid-purple fluorescence.

Hydrozincite (CERTAIN): Hydrozincite occurs on the dump, most commonly as spots or small patches on calcite but sometimes as more extensive coatings. It has a bright blue fluorescence, SW, and a less intense white fluorescence LW. Hydrozincite is an alteration product, forming from zinc-rich minerals upon exposure to the elements. It appears to form most commonly from sphalerite, and I have observed that the pieces that I have collected usually have some sphalerite mixed in (fl. orange, LW). I have found hydrozincite associated with pieces that had a lot of zincite in them as well.

Microcline (CERTAIN): Fluorescent microcline is, to me, one of the more interesting minerals that can be found fairly easily on the dump. The microcline ranges in daylight color from gray or white to bright green (amazonite). A lot of the microcline is fluorescent, but the fluorescent response varies considerably from a very dim blue-gray SW, or dim blue-white SW, up to a much brighter powder-blue fluorescence SW (no LW fluorescence, as far as I know). Some of the microcline does not fluoresce at all. The bright fl. blue material is definitely uncommon, and the best specimens that I have found are associated with fl. orange-red calcite, and brown andradite and the microcline itself is some shade of green in daylight color. The two-color combination, blue and bright orange-red, can be quite attractive. Another interesting combination is microcline with a less intense blue-gray fluorescence associated with calcite (fl. orange-red), willemite (fl. green) and a glassy light-gray quartz. A piece of the better-quality fluorescent blue microcline, associated with orange-red fluorescent calcite and andradite, is illustrated here:


Microcline (blue) with calcite (red) and andradite, SW


Less commonly, microcline can be found with a red or pink fluorescence. The pink-fluorescent material, in particular, has been referred to as “pink amazonite” by other collectors although the material is gray in ordinary light. I have found a few pieces that feature it associated with the ordinary green microcline with the blue-gray fluorescence, hornblende, willemite, and calcite (see picture, below). The gray grains of “pink amazonite” are distinctly separate from the green microcline, indicating perhaps that it is a different type of feldspar, such as hyalophane or a plagioclase. The material does appears to be a feldspar of some sort: it has the right cleavage angle and hardness and does not dissolve in acid. The powdered mineral also retains its fluorescence after a long soaking in hydrochloric acid (so not due to included calcite).


Microcline (pink, blue-gray) with willemite (green) and calcite (red), SW


Phlogopite (CERTAIN): Part of the original “waste” rock that was dumped onto the Buckwheat Dump included some of what is often called "limestone", but is in fact the Franklin Marble. In the marble, crystals of phlogopite mica can be found in shades of gold, coppery-brown and dark brown colors. Some of this phlogopite fluoresces, with a soft golden fluorescence, SW only; typically it is the lighter-colored phlogopite that has the fluorescence. The fluorescence appears to be the best on the edges of the sheets of mica. The phlogopite is often associated with cream-white fl. tremolite or bright blue-white fl. diopside in the marble; small flecks of graphite are also a common associate. The accompanying picture shows an attractive crystal of phlogopite under SW, embedded in marble, with smaller amounts of tremolite and diopside:


Phlogopite crystal (gold), diopside and tremolite (white) in marble, SW


Scheelite (POSSIBLE): Scheelite is known to occur on the Buckwheat Dump, rarely. The material that I found was as small (2-3mm) grains in a rather dark-colored matrix rock with microcline and small amounts of calcite (fl orange-red) and willemite (fl green). The fluorescence was a moderately bright yellow, SW. My identification of this material as scheelite is questionable; it seems the most likely possibility since there was no obvious molybdenite in the specimen but the material still could be powellite, or titanite, or something else.

Sphalerite (CERTAIN): Sphalerite, with a characteristic orange fluorescence that is best LW, can be found as light-colored grains (“cleiophane”) and sometimes as veins and masses with a sparkling (“adamantine”) luster. I have found sphalerite on several occasions, associated with fluorite (fl. blue-green) and fluorapatite (fl. orange) in a dark-colored matrix, or sometimes with willemite and franklinite in a very light-pink non-fluorescent carbonate matrix (probably dolomite). Sphalerite is most commonly fl. orange, but some of the material is also fl. bright blue, sometimes in the same grain with the orange fluorescence. The fluorescence (orange or blue) appears to be best under LW light, but is certainly easily visible under SW as well and makes an attractive combination with the green fluorescence of willemite. The orange-colored sphalerite also has a very pronounced phosphorescence (LW). The piece shown in the following picture, collected on the Buckwheat Dump in the 1990’s, features grains of sphalerite embedded in a matrix with franklinite and fluorite. The sphalerite has a bright orange fluorescence, and the fluorite has an attractive light blue fluorescence under longwave UV:


Sphalerite (orange) with fluorite (orange), LW


Tremolite (PROBABLE): I have collected several pieces of the crystalline, white Franklin Marble that is sometimes referred to as “limestone". In this material one can sometimes find glassy white grains of a mineral that has a moderate to fairly bright cream-white fluorescence SW. This, I have been told, is tremolite and is to be distinguished from similar-appearing material that has a bright blue-white fluorescence that is diopside (see diopside). The two minerals (apparently) can occur in the same piece of marble but I have not tested the tremolite chemically. In one piece where I had a fairly large grain of the material, I made careful observations of the cleavage angle and it appeared to have the 120-80 degree cleavage planes under a spotlight that would indicate an amphibole (i.e. tremolite). The tremolite is often associated with fluorescent phlogopite mica, and I have found several pieces of this material on more than one occasion.

Willemite (CERTAIN): Willemite, of course, is one of the most abundant fluorescent minerals to be found at Franklin and Sterling Hill, and the combination of fluorescent-green willemite with red calcite is known worldwide. Willemite is quite abundant on the Buckwheat Dump. The daylight color of this willemite is most commonly some shade of red or red-brown, usually associated with gray calcite. The fluorescence of this reddish willemite is green, best under SW, but unfortunately it does not often have the brilliant intensity of fluorescence that the best of the Franklin willemites are known for. The willemite with the brightest fluorescence comes from material that is naturally green in color (in daylight). This green willemite can be found on the Dump, associated either just with black franklinite or with franklinite and calcite, making for brilliant fluorescent combinations, but it is not as easy to find and some digging or careful, systematic searching will be required to turn up cabinet-sized specimens. Occasionally one can find a piece of the granular, green willemite associated with black franklinite and bright red zincite. Other, more unusual types of willemite that I have found include the so-called “grape” willemite, with a reddish purple color and brilliant green fluorescence, and coatings of white willemite. This white willemite has been described as being secondary in nature, and typically has, in addition to the usual bright green SW fluorescence, a very long-lived phosphorescence when the lamp is turned off.

And there are other fluorescent minerals to be found on the Dump which I have not had the good fortune to find myself; cuspidine is probably the most sought-after of these. It was a bit disappointing for me to find that there were so few detailed on-line references to the Buckwheat Dump and what, specifically, can be found there (the one exception being Chris Thorsten’s excellent website, www.njminerals.org) My own observations on what can be found are somewhat limited, since I cannot collect there frequently, but I hope by sharing them I will encourage other collectors (some, hopefully, with more experience) to publish their own observations. Collecting at the Buckwheat Dump is a fascinating, ever-changing experience and I hope to be back many times in the future. For those who go, learn all you can first and your trip will be that much more rewarding and enjoyable when you get there.

*Sterling Hill, another fabulous collecting locality for fluorescent minerals, is not as well-known to me and is in any case a proper subject for a separate monograph.


BIBLIOGRAPHY

Jones, Robert W., "Nature's Hidden Rainbows", UVP, Inc., 1970

Pough, Frederick H. "A Field Guide to Rocks and Minerals (Peterson Field Guides)", Houghton Mifflin Harcourt, 1998

Robbins, Manuel A. "Collector’s Book of Fluorescent Minerals", Springer, 1983





Article has been viewed at least 11201 times.

Comments

In order to leave comments to this article, you must be registered
Mineral and/or Locality  
Search Google  
Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
Current server date and time: December 19, 2014 13:40:10
Mineral and Locality Search
Mineral:
and/or Locality:
Options
Fade toolbar when not in focusFix toolbar to bottom of page
Hide Social Media Links
Slideshow frame delay seconds