ADAMITE

Zn₂(AsO₄)(OH),
zinc arsenate hydroxide

The early history of adamite from the Franklin-Sterling Hill area is one of confusion.  It was first reported, erroneously, from Sterling Hill (Edwards, 1971) but was ascribed to the wrong assemblage, which in turn led to an incorrect locality attribution.  The locality was later corrected to the 500 level at Sterling Hill, where adamite was described as a secondary hydrothermal vein mineral, ranging in color from “lemon yellow to light orange” (Edwards, 1972b) and mixed with secondary zincite of similar color.  The suggested presence of adamite in these veins came about through a positive microchemical test for arsenic by George Pigeon (a noted collector of the local minerals), combined with the pale yellow-green LW fluorescence of the material, which some likened to that of adamite from the Ojuela mine in Durango, Mexico.  Though Pigeon obtained positive tests for arsenic in five of fourteen specimens examined, repeated x-ray tests (Edwards, 1972c, 1973; Cook, 1973) failed to disclose the presence of adamite.  It was thus assumed that Pigeon’s tests were in error, and the notion of fluorescent adamite from Sterling Hill was soon abandoned, much to the chagrin of collectors who had invested heavily in this material as specimens were coming out.

There the matter rested until 2017, when reinerite, a zinc arsenite mineral of composition Zn₃(AsO₃)₂, was described from the same assemblage (Bostwick and Verbeek, 2017; Horste, 2017).  Shortly after publication of those papers, Peter Chin (written commun. to Verbeek) speculated that reinerite might have been the source of Pigeon’s positive tests for arsenic.  Thus the much-maligned Pigeon might have been partly correct after all:  arsenic was indeed present in some of his analyzed samples, but it resided not in adamite as supposed, but in reinerite, a mineral unknown until 1958 and probably not familiar to anyone on the Franklin scene during the 1970s.  Redemption can take decades…

Authentic adamite from Sterling Hill was first reported by Frondel (1972), citing an unpublished 1971 study by David K. Cook, then a graduate student in mineralogy at Harvard.  Cook’s work was also the source of a note by Edwards (1972a) of adamite from Franklin, which was based on specimen #89973 in the Harvard collection.  Both occurrences were formally reported (as cuproadamite) by Cook (1973) in The Mineralogical Record.  The Sterling Hill adamite occurred as “pale green to yellow-green coatings and crystal rosettes” in association with cuprite, chrysocolla, and willemite—a wholly different assemblage from that described above—while the Franklin material, two specimens of which were then known, was of pale to dark green crusts of cuprian adamite with azurite on highly altered calcite matrix.

Since then, adamite has been reported from additional assemblages, most of them from Sterling Hill.  Dunn (1995, p. 653-654) provided brief descriptions of several of these, and Jenkins (unpub. data, 1994) described several more.  Dunn’s reference to “bright pink and deep yellow adamite” from 340 level at Sterling Hill was at first puzzling.  No details were given of this occurrence, nor was it mentioned who reported it.  At first we suspected that the bright pink and deep yellow material might refer instead to miguelromeroite and legrandite, respectively, both arsenate minerals that are known to occur in this area. However, a specimen of purplish-red crystals in the collection of the Franklin Mineral Museum (specimen FMM-5113) was analyzed and gave definitive Raman spectra for adamite.  A second specimen (FMM-5002), of flat sprays 1-2.5 cm across of orange-pink crystals, labeled miguelromeroite, similarly provided strong Raman spectra establishing the claimed identity as correct.

References

Bostwick, R.C. and Verbeek, E.R. (2017), Reinerite added to the 2017 list of “Mineral species found at Franklin and Sterling Hill, New Jersey.”  The Picking Table, vol. 58, no. 2, p. 9-10.

Cook, D.K. (1973), Recent work on the minerals of Franklin and Sterling Hill.  Mineralogical Record, vol. 4, p. 62-66. [Describes adamite (as cuproadamite) from Franklin, and casts doubt on presence of adamite in the secondary zincite specimens from Sterling Hill]

Dunn, P.J. (1995), Franklin and Sterling Hill, New Jersey:  the world’s most magnificent mineral deposits.  Privately printed, 755 pp. [Description of adamite on p. 653-654; mention of cuprian, manganoan adamite in wallkilldellite assemblage on p. 684]

Edwards, F.Z. (1971), Adamite.  The Picking Table, vol. 12, no. 2, p. 5-6. [First mention of adamite from the local area (Sterling Hill), but ascribes it to the wrong assemblage]

Edwards, F.Z. (1972a), Franklin Mineral Notes:  Adamite.  The Picking Table, vol. 13, no. 1, p. 7.  [First mention of adamite from Franklin; see Cook (1973)]

Edwards, F.Z. (1972b), Franklin Mineral Notes:  Adamite (Sterling Hill).  The Picking Table, vol. 13, no. 1, p. 9-10. [Corrects the assemblage error of Edwards (1971) and gives the Sterling Hill adamite locality as the 500 level, as “admixtures with zincite in calcite veins cutting the ore”]

Edwards, F.Z. (1972c), Additional Franklin/Ogdensburg Mineral Notes.  The Picking Table, vol. 13, no. 2, p. 7.  [States that fluorescent adamite from 500 level at Sterling Hill has not been validated; x-ray work shows mixtures of willemite and zincite instead]

Edwards, F.Z. (1972d), The Picking Table, 1972, vol. 13, no. 2, p. 9.  [Short description of purported adamite from 960 stope, 340 level at Sterling Hill; see photo ADM3b]

Edwards, F.Z. (1972e), The fluorescent minerals of the Franklin/Ogdensburg area.  The Picking Table, 1972, vol. 13, no. 2, p. 11.  [Describes fluorescence of Sterling Hill “adamite,” later shown to be secondary zincite]

Edwards, F.Z. (1973), Adamite/fluorescent zincite.  The Picking Table, 1973, vol. 14, no. 1, p. 9-10.  [Mentions that numerous x-ray scans of purported adamite from the 500-level occurrence at Sterling Hill failed to verify the presence of that mineral]

Horste, James (2017), The story of Sterling Hill reinerite.  The Picking Table, vol. 58, no. 2, p. 11-12.

King, V.T., King, N.E., Betancourt, P.P., Bostwick, R.C., Chin, Peter, Hecht, T.J., Kuitems, S.M., Moritz, Harold, Nemetz, J.D., Nikischer, A.J., Sanford, Stephen, Van Fleet, J.A., and Verbeek, E.R. (2021), The Mineralogy of Franklin and Ogdensburg, New Jersey—A Photographic Celebration. Privately published, 1400 pp. [Photographs of adamite on p. 758-759]

Parker, Fred J. (1982) Arsenate minerals of the Sterling Hill mine [New Jersey]: an overview. The Mineralogical Record, vol. 13, no. 1, p. 35-38.

Images