Franklin and Sterling Hill, New Jersey, USA – table of longwave fluorescent minerals

Filed under: regular postings,rockhounding maps — Gary December 18, 2006 @ 6:09 pm

alleghanyiteAlleghanyite is an exceptionally rare member of the humite group, and this specimen is unusually rich with gemmy brown microcrystals to 2 mm flatlaying along an approximately 3-cm vertical axis on this specimen . The matrix is a typical mix of franklinite/calcite/willemite and is highly fluorescent.

The mines of Franklin and the Sterling Hill Mine at Ogdensburg, Sussex County in northwestern New Jersey are world famous and deservingly so. No other site can boast the same assortment of rare and interesting minerals. Over three hundred different minerals were found at these mines and most are listed in The Minerals of Franklin and Sterling Hill Table.

The Franklin and Sterling Hill mines have been known to produce specimens of:

  • Elements Class:
    • arsenic, copper, gold, graphite, lead, silver and sulfur.

  • Sulfides Class:
    • acanthite, arsenopyrite, bornite, breithauptite, carrolite, chalcopyrite, covellite, cuprostibite, digenite, djurleite, domeykite, galena, gersdorffite, greenockite, hawleyite, lollingite, marcasite, molybdenite, nickeline, pararammelsbergite, pyrite, pyrrhotite, rammelsbergite, realgar, safflorite, skutterudite, sphalerite, stibnite and wurtzite.
  • Sulfosalts Subclass:
    • baumhauerite, berthierite, seligmannite, tennantite, tetrahedrite and zinkenite.

  • Halides Class:
    • atacamite and fluorite.

  • Oxides Class:
    • anatase, aurorite, birnessite, brookite, brucite, chalcocite, chalcophanite, cianciulliite, corundum, cryptomelane, cuprite, feitknechtite, franklinite, gahnite, goethite, groutite, hauckite hausmannite, hematite, hercynite, hetaerolite, hydrohetaerolite, jacobsite, lawsonbauerite, magnetite, manganite, manganosite, mooreite, pyrochroite, pyrophanite, romeiite, rutile, spinel, todorokite, uraninite, woodruffite and zincite

  • Carbonates Class:
    • aragonite, aurichalcite, cerussite, dolomite, dypingite, hydrotalcite, hydrozincite, kutnohorite, loseyite, malachite, monohydrocalcite, otavite, pyroaurite, rhodochrosite, rosasite, siderite, sjogrenite, smithsonite, strontianite and znucalite.
  • Borates Subclass:
    • cahnite, canavesite, fluoborite, mcallisterite, roweite and sussexite

  • Sulfates Class:
    • anglesite, anhydrite, antlerite, barite, bassanite, bianchite, brochantite, celestite, connellite, charlesite, devilline, epsomite, erythrite, ferrimolybdite, gypsum, halotrichite, hexahydrite, huebnerite, linarite, mooreite, orthoserpierite, powellite, scheelite, serpierite, spangolite, starkeyite, thaumasite, torreyite and wulfenite.

  • Phosphates Class:
    • apatite, descloizite, meta-ankoleite, monazite-(Ce), newberyite, niahite, pyrobelonite, turneaureite, wallkilldellite and wendwilsonite
  • Arsenates Subclass:
    • adamite, adelite, akrochordite, allactite, annabergite, arseniosiderite, bementite, austinite, brandtite, chlorophoenicite, clinoclase, duftite, euchroite, eveite, flinkite, fluckite, guerinite, haidingerite, hedyphane, holdenite, jarosewichite, johnbamite, kolicite, kraisslite, legrandite, liroconite, magnesium-chlorophoenicite, magnussonite, manganberzeliite, manganese-hornesite, mcgovernite, metalodevite, meta-zeunerite, mimetite, ogdensburgite, ojuelaite, parabrandtite, parasymplesite, pharmacolite, pharmacosiderite, picropharmacolite, retzain-(La), retzain-(Nd), sarkinite, scorodite, sterlinghillite, synadelphite, tilasite, uranospinite, villyaellenite and yukonite

  • Silicates Class:
    • actinolite, aegirine, albite, allanite-(Ce), alleghanyite, almandine, analcime, anandite, andradite, anorthite, anorthoclase, apophyllite, augite, axinite, bakerite, bannisterite, barylite, barysilite, bementite, biotite, bostwickite, bultfonteinite, bustamite, caryopilite, celsian, chabazite, chamosite, chloritoid, chondrodite, chrysocolla, chinochlore, clinohedrite, clinohumite, clinozoisite, clintonite, cummingtonite, cuspidine, datolite, diopside, dravite, edenite, epidote, esperite, ferro-actinolite, fraipontite, franklinfurnaceite, franklinphilite, freidelite, gageite-1Tc, gageite-2M, ganophyllite, genthelvite, gerstmannite, glaucochroite, goldmanite, grossular, hancockite, hardystonite, hastingsite, hedenbergite, hemimorphite, hendricksite, heulandite, hodgkinsonite, hornblende, humite, hyalophane, illite, jerrygibbsite, johannsenite, junitoite, kaolinite, kentrolite, kittatinnyite, kottigite, larsenite, laumontite, lennilenapeite, leucophoenicite, magnesioriebeckite, manganhumite, manganpyrosmalite, margarite, margarosanite, marialite, marsturite, meionite, microcline, minehillite, muscovite, nasonite, natrolite, nelenite, neotocite, nontronite, norbergite, olivine, oligoclase, orthoclase, pargasite, pectolite, pennantite, petedunnite, phlogopite, piemontite, pimelite, prehnite, pumpellyite, pyroxmangite, rhodonite, richterite, roeblingite, samfowlerite, sauconite, scapolite, schallerite, schorl, sclarite, sepiolite, serpentine, sillimanite, sonolite, sphene, spessartine, stilbite, talc, tephroite, thomsonite, thorite, thortveitite, tirodite, tremolite, uranophane, uvite, vesuvianite, willemite, wawayandaite, wollastonite, xonotlite, yeatmanite and zinalsite

    bold – indicates that either Franklin or Sterling Hill is the type locality for that mineral.

    Over 60 new minerals to science were also described from samples taken from these mines, thus claiming these mines as their type locality (these minerals are shown in bold in the table). While other great localities can have similarities with other sites, there simply are no real good parallels with the mineral assortments of Franklin and Sterling Hill, New Jersey.


    The geological reasons for this diversity of minerals is somewhat complex. It involves zinc, manganese and iron rich sediments on a pre-Cambrian sea floor being swept up into a regional orogenic event that created a mountain chain in the approximate position of the current Appalachian Mountains. This event however occurred more than a billion years ago. The origin of the zinc, manganese and iron sediments is theorized to have been manganese nodules and/or sulfide producing “black smokers” that we see along mid-oceanic ridges today. Whatever the case, the manganese and zinc is what drives almost all of the unique and exotic mineral species that are found here. Later contact and regional metamorphism, hydrothermal alterations and weathering produced unusual results and thus a whole “mess” of rare zinc and manganese minerals.

    The minerals that were found here are unlike those found anywhere else. Unusual manganese and zinc oxides and silicates as well as a few arsenates, are the hallmark of this locality. The primary ore minerals are the franklinite (an iron, zinc and manganese oxide) and willemite (a zinc silicate) and to a lesser extent zincite (a red colored zinc oxide) and hemimorphite (a zinc silicate). Iron is the primary product, in terms of weight, while zinc and manganese are rather significant.

    When first exploited, it was thought that the ore minerals were magnetite (an iron oxide) and cuprite (a red colored copper oxide), but the ore behaved differently than other magnetite ores in the smelting process and the “cuprite” yielded no copper. Of course most of the “magnetite” turned out to be a new mineral to science, franklinite and the “cuprite” turned out to be zincite, one of the first new minerals identified in the New World and one of many to come from this locality. As the mining continued, more uses and better techniques for the exploitation of zinc and manganese were found and the mine became a boom for the area. The steel, paint and coal industries (needed to smelt the ore) were all positively affected by these mines. The iron/manganese alloys strengthened steel; while the zinc was used in a variety of paints and in certain alloys.


    sterling_hill sterling_hill_2

    There are several ways that minerals can emit light, besides the light that is emitted from exposure to daylight or the light from normal light bulbs. Some of these ways involve special lamps that emit non-visible ultraviolet light (at least not visible to humans). The light from these ultraviolet lamps reacts with the chemicals of a mineral and causes the mineral to glow; this is called fluorescence. If the mineral continues to glow after the light has been removed, this is called phosphorescence. Some minerals will glow when heated; this is called thermoluminescence. And there are some minerals that will glow when they are stuck or crushed; this is called triboluminescence.

    The fluorescent minerals are minerals that emit visible light when activated by invisible ultraviolet light (UV), X-rays and/or electron beams. Certain electrons in the mineral absorb the energy from these sources and jump to a higher energy state. The fluorescent light is emitted when those electrons jump down to a lower energy state and emit a light of their own. Although most collectors do not have access to X-ray or high energy electron emitters, they do have access to affordable ultraviolet lamps. The visible light emitted after being activated by UV light is sometimes very colorful and can often be very different from the normal color of the mineral. Collecting fluorescent minerals is a popular hobby and experienced collectors can use fluorescence for identification purposes. At night or in dark mines or caves, fluorescence can be used to find certain mineral deposits and is a viable prospecting technique.

    There are two kinds of ultraviolet light, longwave and shortwave. Longwave UV light is known as “black light” and most people are familiar with its effects of making white clothing glow in the dark. This is due to whitening chemicals in detergents. Remember the slogan “Whiter than white”? See the table of longwave fluorescent minerals.


    Shortwave UV light is by definition of a shorter wavelength than the longwave UV light. Shortwave lamps which are available to collectors, can be very entertaining and useful to identify minerals, however it is dangerous to look at the shortwave light source (it can cause blindness) and they should not be used without adult supervision. See the table of shortwave fluorescent minerals. A lamp that can emit longwave and shortwave light is preferred as many fluorescent minerals emit different colors under different wave lengths and some only fluoresce under one but not the other.

    Activator elements are responsible for fluorescence. But not all specimens have these activator elements. Care in identifying minerals, using UV fluorescence, should therefore be taken. Some minerals will have consistent colors as in they will always fluoresce red for example while other minerals may have many different colors from one locality to another. Also, one specimen may fluoresce and another specimen of the same mineral may not fluoresce at all. So how can fluorescence help in identifying minerals?

    Well, fluorescence is not a common phenomenon being found in only certain minerals. If two minerals are similar and yet one is listed as a possible fluorescent mineral, a fluorescence test could prove important. However if an unknown mineral does not fluoresce, it should not so quickly be dismissed as not being the suspected fluorescing mineral, unless that mineral is reported to always fluoresce. Fluorescence is not usually an absolute property found in all specimens of even a named fluorescent mineral, but there do exist some minerals that are so reliably fluorescent that fluorescence is the best test to use. The tables below include the more common fluorescent minerals that are popular with collectors. Compare the minerals found in different wavelengths and in different colors.

    is a very special trait to many of the minerals here. In fact the city of Franklin calls itself “The Fluorescent Mineral Capital of the World”! Not all the minerals fluoresce, but many do, especially willemite and calcite. It is hard to imagine a single fluorescent mineral display that exists without at least a specimen from Franklin or Sterling Hill. The most ordinary and even dull looking specimens from these localities can literally light up with beautiful reds (calcite) and greens (willemite) under short-wave and long-wave ultraviolet light. These specimens are made even more interesting with a sprinkling of nonfluorescent black franklinite peppering the fluorescent display with opaque black dots. Other fluorescent minerals from here include esporite (bright yellow-green), clinohedrite (orange-yellow), hardystonite (violet-blue), barite (white), manganaxinite (an intense red) and over 70 others.

    Manganese is the typical activator, either as a trace element or as a primary element in the fluorescent mineral’s chemistry. The ore body at Franklin and Sterling Hill is surrounded by a marble made up of mostly calcite similar in appearance to the calcite of fluorescent fame. Only a few meters from the ore body however, the calcite is non-fluorescent. It lacks the manganese as an activator. This tells geologist how far the manganese permeated into the surrounding rocks.

    Several minerals from this site have been cut as gemstones. Many rank as the largest gemstones of their kind in the United States and the world. Although most are not nor have ever been significant on the gemstone markets, they were cut by and for gemstone collectors who seek unusual gemstones. Willemite, zincite, rutile, hodgkinsonite and friedelite are a few of the rare gemstone minerals that have been cut for collectors and museums from here.

    Sadly, the mines are now closed and filled with water and rock. Only a few mine dumps remain to provide any new material. Two museums are present to educate the public about these remarkable mines and one allows tours into some of the actual mine shafts and both provide mine dump collecting opportunities. It is easy to see that these mines are truly one of the best mineral localities to ever be discovered and specimens from them should be treasured.

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