HOLDENITE, a NEW ARSENATE of MANGANESE and ZINC, from FRANKLIN, NEW JERSEY Cuanrps Paracnn Enp E

144 THE AMERICAN MINERALOGIST

HOLDENITE, A NEW ARSENATE OF MANGANESE AND ZINC, FROM FRANKLIN, NEW JERSEY Cuanrps Paracnn enp E. V. SrreNNorvl. The single specimen on which the mineral here described has been seen was found in the collection of A. F. Holden, fifteen yearsago, mistakenly labelledleucophoenicite. Crystals were then measuredby the seniorauthor and practical certainty was reached that they representeda new arsenateof manganese.To determine its chemical nature, however, it would have been necessaryto removemost of the material from the only specimen. In the many ensuingyears, continued searchfor more examplesof the mineral proved fruitless. The resolution was finally reached that the sole specimenmust be sacrificedand this was done, all but two or three crystals being detached. The material so obtained has been analyzed by the junior author, the result confi.rmingthe conclusionthat the mineral is a distinct species. Holdenite is orthorhombic with the axial ratio: aib:c:.3802:l:.2755. p0:.7230. qo:.2755. Sevencrystals were measuredgiving concordantresults in angular values from a complex form seriesas shown in Table 1. The crystalsare tabular parallel to the facetaken as the macropinacoid, the largest one on the specimen measuring 8 mm. in greatest diameter.

Figure 1. Crystal of Holdenite 1 Published by permission of the acting Secretary of the Smithsonian Institution. IOI]RNAL MINERALOGICAL SOCIETY OF AMERICA 145

Teer,n I. Fonus lwo ANcrBs oF HoTDENTE.

Number of Calculated Angles Measured (average) Angles Symbol faces crysts d Limits p Limits c (001)p 1 1 00'00' 00'00' 00'00' o (100)p 7 1 90 00 90 00 90 00 b (o1o)" 7 7 00 00 00 00

(ll0) p ( 69 12 m 20 7 69 08 -4

t1 r (t20) p z 2 52 +t 52 46 Tr

| 1a (130)p A A 4r t2 n 41 10 I e (011) 00 00 l5 2+ 00 00 05 41 +16 -10

_f(o:r; 39 34 00 10 39 33 +2 -2 d (r02) 90 00 20 03 90 00 20 02 +1 -l p $rt) 69 08 37 44 69 lL +r2 37 47 +8 -9 -4

q (211) 79 13 55 49 5548 +r2 -4 -2

(311) 82 44 +6 65 2+ r 82 46 65 26 1i +3

J-7 (131) 41 08 47 4l s 47 4l -4 +7 -lJ za(151) 274r 57 16 27 28 +4 57 18 +7 -5 -8 t (2sr) +6 23 63 2+ 46 20 63 32 +15 -10 -9

* (182) 18 10 49 t4 t8 12 +14 48 55 +1s -t4 -t6

_L 1') 49 23 /J JJ tJ u (7.t6.2) 46 J/ 73 24 -12 _J t46 TH E AMERICAN MINERALOGIST

The crystals vary little in habit and most of the forms occur on all of them as shown in Table 1. The base, c was seen but once and n and e were found on but two crystals. The forms I w and r were also found but once,all on the most complexcrystal measured which is shown in the figure. There was, however, a form present on all the crystals with relatively large faces which varied widely in its angular position. This is the pyramid z to which has been assignedthe symbol (7.16.2). As shown in the figure this form is in a zone with I and s; and the anglesas found on this one crystal agree well with the calculated values. On other crystals, however, the value of S varied fuom 47" l4t to 54" 36' and that of p from 72" 70' to 76o06'. The symbol (a91) is simpler in form and alsolies in the zone with I and s; but while the value of 4 for it, 49" 23', agreesexactly with the best measured angle, the p angle is two degreestoo large and the preferencewas thereforegiven to the more complex symbol. Holdenite has a poor cleavageparallel to the brachypinacoid. Its hardness is 4 and the specific gravity, determined by floating in Clerici solution, is 4.07. The color varies from clear pink to deep red and yellowish red. Biaxial (f ). The plane of the optic axes is parallel to (010) with the acute bisectrix emerging normal to (100). 2V:30" 20' (measured),28o 58' (calculated). Dis- persion easily perceptible,p)2.

otll to c a:1.769 Allto b p: r.770 7ll to a t:I.785 We are indebted to ProfessorLarsen for the index values, determined by the immersionmethod. About 0.42 gr. of fairly pure material was prepared by Mr. Berman for the analysis. It contained willemite and calcite as impurities. 1. Analysis of Holdenite by E. V. Shannon. 2. Molecular ratio of 1. 3. Molecular ratio after eliminatins willemite and calcite. JOURNAL MINERALOGICAL SOCIETY OF AMERICA r47

1. Per cent sioz 2.01 .033 AszOs 17.4O .076 .076 .076:lx 076 MnO 37.75 .532 .532 FeO 1.80 .025 .025 ZnO 28.08 .345 279 .914:02X.076 CaO 3.80 .067 .042 MeO 1.45 .036 .036 HrO 6.62 ..to/ .367 .367-5X..073 PbO trace MnzOs trace AlzOa trace

98.91 The presenceof calcite in the sample was proved optically and by effervescenceof grains on solution in acid' The sample,however, was not sufficiently large to permit determination of COz. We assumethe deficiencyof the analysis, 1.097a,to be COr and take enoughof the CaO to satisfy this as CaCOa' We regard the SiOg as due to willemite and take sufficient ZnO to satisfy this compound. On this basis there was 7.38/6 of willemite and 2.497a of calcite in the sample. Deducting these from the analysis we obtain the ratios of column 3 above which leadsto the formula for holdenite 12R/'O'AszOs'5HrO' Manganeseand zinc are presentin the proportion of approximately 2:1. The formula may then be expandedto the form SMno'4zno' As2ob'5H2o which requiresthe following composition: AszOs 18.96 MnO 46.78 ZnO 26 83 HrO , :t 100.00 Holdenite is thus a very basic arsenateof manganeseand zinc. The only mineral at all resembling it in composition is the recently described minbral chlorophoenicite, also from Franklin, to which was assignedthe formula 10R"O'AsgOs'7HzO with R" chiefly manganeseand zinc in the proportion ol 3:2. 148 TH E AM ERICAN MI N ERALOGIST

Holdenite is named in honor of A. F. Holden in whose splendid collection now at Harvard University the unique specimen of this mineral was discovered. This was a slab of massive franklinite ore with a slickensided surface 10 by 7 cm. in dimensions, clearly one wall of a narrow veinlet. The crystals of holdenite were attached for the most part directly to the vein wall or to a thin coating of manganiferous calcite. With it was associatedbarite, galena, pyrochroite and f,brous willemite, all in minute amount.