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THE AMERICAN MINERALOGIST, VOL 51, SEPTEMBER_OCTOBER, 1966 ZINCIAN AEGIRINE-AUGITE AND JEFFERSONITE FROM FRANKLIN, NEW JERSEY Cr.rrnonoFnoNnBr eNn Jux ho, Departmentof Geolog,icalSciences, H arsaril [] niaer sity Cambrid. ge, M as s a chu s e tt s.r Agsrnect A coarsely crystallized dark colored monoclinic pyroxene found abundantly in skarn zones at Franklin and Sterling Hill, New Jersey, has long been known under the name jefiersonite. It has been classed as a diopsidic pyroxene, but four new chemical analyses (with accompanying r-ray and optical data) establish that it comprises highly zincian and manganoan members of a series from aegirine-augite to sodian and ferrian augite. Both Mn2+ and Zn are much in excess of Fe2f, with almost 40 atomic per cent Mn in the B position in one analysis. As Fea+and Na decrease the color changes from reddish brown and mahogany brown to dark olive green and greenish black. The original jefiersonite of Vanuxem and Keating (1822) probably referred to the latter material; the name lacks species or varietal significance and may be set aside. INtnooucuoN Three different types of pyroxene have been found in the so-called skarn zones in the orebodiesat Franklin and Sterling Hill, New Jersey. The most common type is a manganoan and sometimes also zincian variety of diopside. It generally contains NInO in the range from 4 to 10 weight per cent (Table 1, anal. 1 to 5). If little or Lo Zn is present,this material has been called schefierite,following the varietal name originally proposedby Michaelson(1863) for manganoandiopside of similar com- position from Langban, Sweden. Variants containing Zn in addition, amounting to about 3 weight per cent ZnO in the reportedanalyses, were named zinc-schefferiteby Wolff (1900). Thesevarieties of diopsideare in generallight colored,ranging from pale buff to light brown and brown and occur in coarsemasses with a basal parting. The secondtype com- prises material relatively high in manganese,falling into the composi- tional field of johannsenite(Table 1, anal. 9, 10). It occursvery sparingly in the samegeneral association, and forms divergent groupsof frbersup to 1 cm or so in Iength that are white, brownish yellow or pale brown in color. A third type of pvroxenealso occurs.It differs in being very dark in color,usually a dark mahoganybrown to brownishor greenishblack, and in possessinga somewhatresinous rather than vitreous luster. It occurs as large anhedral masseswith an indistinct prismatic cleavageand as coarsecrystals, up to a foot in size,of a typical augite habit. This mate rial passesunder the name jeffersonite,although, as noted beyond, its I Mineralosical Contribution No. 4241. t$6 ZTNCIAN AI'GIRINE AUGITN AND JIJFFERSONITF:. 1n7 Tenr,r 1. Omrn ANer-vses ,lNo Oprtcer, CoNsre,Nrs on PvnoxnNrs rnou FnaNrlrl 1. +. 5. 6. 7. 8. o 10 Sioz 52 06 51.20 52 86 51 70 49.91 45 95 49 03 50 30 48 29 AlrOs o ?7) - -'t 10R 36 1.93 0 85 0.86 FezOa 1.sOJ 4 )'.) l'eo 1.41 165 10.53 8 91 3.95 2.59 tr MnO 4 57 996 5.31 7.43 6 86 7.00 10.20 7.9r 14.85 26.10 ZnO 3.38 3 31 3.01 4.39 10.15 7.r4 327 MeO 15.56 12.70 13.24 12.57 8.18 3.61 5.81 6.19 2.84 CaO 26.30 2l 09 24.48 23.68 15.48 21.55 1988 22.97 22.s9 NarO 009 0.12 HzOf 1.35 0.45 0.65 0.35 0.70 Rem. 032 t.20 0.60 Total 99.90100.13 100 80 100.19 98.82101 .57 100.rO rOO.r7 99.82 s.G. 3.39 3 31 3.63 3.55 3.52 q 1.673 1.690 1 676 .697 r.699 p 1.680r.699 1.683 .706 r.7t2 a 1 700 1 72r 1.705 r.723 .725 1.734 2V 60'+1" 60' 60" zAc 37"+1" 43" 46" 1. Diopside. Franklin. Jenkins and Bauer, analysts, cited by Palache (1937). FeO includes AI:O:. 2. Schefierite. Sterling Hill. Schaller, analyst, cited in Palache (1910). Recalculated to 100 after deducting 0.43 COz as CaCOa. Rem. is F 0.32 3. Zinc-schefierite. Franklin. Wolff (1900). 4. Zinc-schefierite. Franklin. Hillebrand (1900). 5 Zinc-schefierite. Franklin. L. H. Bauer, unpublished analysis. 6. Jeffersonite. Franklin. Hermann (1849). 7. Jeffersonite. I'ranklin. Pisani (1873). 8. Jefiersonite. Franklin. Steiger, analyst, cited in Palache (1910). Rem. is HzO-. Re-analysis cited in Table 2. 9. Johannsenite. Franklin. Fairchild, analyst, cited in Schaller (1938). 10. Johannsenite. Franklin. Bauer, analyst, cited in Frondel (1965). identity with the original jeffersoniteof Vanuxem and Keating (1822)is uncertain.It has been classedhitherto as a diopsidic pyroxene,distin- guishedfrom schefferiteby the presenceol Zn and of more than traces of Fe (Palache,1937). Older analysesattributed to jeffersoniteare given in Table 1, analyses6 to 8. A survey of numerous specimensof this mineral preservedin the Harvard collectionshas now establishedthat it contains variable and sometimes large amounts of trivalent iron and of sodium, and representsa solid solution extending from aegirine-augiteto sodian and ferrian varieties of augite (Table 2, anal. 1 to 5). Considerable amounts of both Mn and Zn arepresent in all specimens.A description of 1408 C. FRONDI]L AND J ITO this material and a review of the history of ieffersoniteis given in follow- ing sections. DnscnrptrorgoF SPECTMENS The dark colored pyroxenes called jeffersonite occur locally in skarn zonesin the orebodiesand are not constituentsof the normal franklinite- willemite-zincite ore. The typical associatedminerals are andradite, rhodonite, hendricksite,bustamite, feldspar, apatite, franklinite, wille- mite and calcite.The indicesof refraction of the jefiersonitevary con- siderably,with 7 (Na) usually in the rangefrom 1.74to 1.78.The highest valueswere observedin dark brownish black and reddish brown masses up to 3 cm in size intergrown with barium feldspar and andradite. Numerousspecimens of this type of material wereobtained in 1954when supporting pillars of ore in the Parker shaft area were mined out. A chemicalanalysis, cited in Table 2, column 1, establishesthis material as a highly zincian and manganoan varietv of aegirine-augite containing about 40 per cent of the NaFeSizOoend-component. A more common type of jeffersonite is a rich mahogany brown to dark brown in color. It often occurs as anhedral grains up to 3 or 4 cm in size with a more or lessdistinct parting, but sometimesis very coarsely crys- tallized. One broken mass showed a parting surface 7 inches across. Another broken single-crystalmass 4X-3X-2 inches in size contained numerous rounded inclusions of calcite and of willemite ranging up to about 1 cm in size.Similar specimenshave beenseen in other collections, and they have been sold in trade under the incorrect name zinc-scheffer- ite. They have a spectacularappearance in ultraviolet radiation, the calcite fluorescingbright salmon pink and the willemite green. An analy- sis of this material, cited in Table 2, column 2, showed that it is an aegirine-augitewith a lower content of Fe3+and Na than the preceding material. Another specimen of this color, the subject of an unpublished analysisby L. H. Bauer, made some years ago, showedjeffersonite as- sociatedwith massivereddish willemite. The original analysisreported all of the iron as divalent, but a redetermination of the iron showed that the bulk of it is trivalent (Table 2, col. 3). The jeffersoniteanalyzed by Steiger(cited in Palache,1910) and here re-analyzed (Table 2, col. 4) has the lowest content of Fe3+ and the highest content of NIg. This material occurs as indistinct crystals em- beddedin pale pink calciteand has a dark olive black rather than brown- ish colorin the hand specimen.The powder is grayishgreen instead of the usual brown. Basal parting is well developed.A number of other speci- mens were observedwith a color gradingfrom dark olive greento a dark brownish olive. All of this material has relatively low indicesof refrac- tion, with y (Na) 7.74-I.75. Five specimensanalyzed for their NIn con- ZI NCI A N A EGI RI N E.A UGI T E AN D J I'FF ERSON IT Ii t409 Tent-r. 2. Cirnlrrcnr,, Oprrclr. lNo X-ne,v Dnre lon Aecrnrmr-Aucrm AND AucrrE nnou FnaNrr,rN 2. J. SiOz 46.38 48.64 46.64 49.28 TiOz 0.10 0.03 tr AlzOr l.Jo |.42 I Oa5 1.22 FezOr 12.90 9.86 7.c6 4.lJ FeO I.JJ 077 1.10 3.74 MnO 7.r8 7.20 11.37 7.20 10.10 ZnO 8.77 6.89 8.40 l -lJ 6.46 Mso 1.18 3.55 3.23 s.90 CaO 14.86 16.65 t7.68 19.86 NurO 4.99 4.09\ 1.05 2.38 KrO 0.18 0.04J o.o2 HrO- 0.25 0.03 HzO-l- 0.55 0.73 Total 100.05 99.90 99.54 100.15 Si 1.904 |.e47) 1.em) 1. es2l Ti .003 r.e73.001 f2.01s fr.os+ fz.ooo AI .066 .067) .0811 .os7J Fe3+ .398 .297I .216 .r24) Fe2+ .046 .026 .038 .1241 Mn .250r.032 .244 .983 .393 .2421r.064 Zn .266 .204 .253 .2261 Mg .072 .2t2 .196 .348) Ca .714) . t tJ .843 Na .31811.034.188 .96r .080 .924 K .oo2) .001 S.G. 59 3.56 3.60 J.J) q .741 1.732 1.714 .751 r.742 t-lzJ a .774 1.763 t. /oJ 1.774 t.752 2V 7Ao zAc -60' -J4- &5J- d(600) 1.564 r.564 1.565 1.569 1.570 d(M0) |.617 r.617 1.621 r.629 1.630 d(22r) 2.514 2.516 2.519 2.524 2.529 l.

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