CanadianMin*alogist Vol.23,pp. 233-20 (1985) ABHURITE, A NEW TIN HYDROXYCHLORIDE MINERAL, AND A COMPARATIVE STUDY WITH A SYNTHETIC BASIC TIN CHLORIDE* JOHN J. MATZKO, HOWARD T. EVANS JR., MARY E. MROSE AND PHILIP ARUSCAVAGE U.S. GeologicalSurve!, Reston,Virginia 22092, U.S.A. ABSTRACT longueur d'onde de l'ultraviolet. Le min6ral sedissout rapi- dement dans I'acide nitrique et lentement dans l'acide r6v&le73.490 (en poids) Abhurite Sn3O(OH)2C12is a new mineral speciesfound chlorhydrique. L'analyse chimique 1.090O et 0.4a/oH, et correspondd la for- in blister-like protuberanceson the surfaceof tin ingots sub- Sn, l5.7YoCl, I L'analyse thermique diff6rentielle mergedin a shipwreckabout l00years ago. The recovery mule Sn3O(OH)2C12. que d6gaged235"C et SnCl2,d 525'C. En site, at a depth of about 35 m, in an arm of the Red Sea montre l'eau se de pr6cessionr6vdlent descristaux known as Sharm Abhur, is located 30 km north of Jiddah, diffraction X, les clichds de gxoupespatial iR3m, R3m ou R32, Saudi Arabia. Abhurite forms tlin, platy, colorless,fragile, rhombo6driques, (0@l). Les donndesde poudre six-sidedcrystals averaging 1.5 mm in diameter. The plates g6n6ralementmaclds selon pour arriver ir une maille 616- show no birefringence, the uniaxial figure is positive, and Guinier-Hiigg furent affindes les parametressont d 10.0175(3)' or is 2.06. No fluorescencefor either shortwaveor long- mentaire heryrgonaledont c/a 4.3937.Les raiesprincipales du clichd wave ultraviolet light was detected.Density Dx4.34, Dm c 44.01\2) L; (m6thode des poudres) en A(Ixrttl)l sont: 4.29 g/mt, The mineral dissolvesrapidly in nitric acid and de diffraction Id 3.634(35X0.1.11),3.404(50X208), slowly in hydrochloric acid. Chemical analysis gives 73.4 4.139(50Xll6), 3.244(3s)(r22), 3.r42(3s)(2r4), wt.Vo Sn, 15.7 Cl, ll.0 O and 0.4 H, which corresponds 3.27r(3s)(zrr\, 2.89 I 5(70)(300), 2. 838 I (25X303), to the formula Sn3O(OH)2C12.Differential thermal anal- 2.9074(3 5)(217), 2.5313(l00xl.l. l5)' Descristaux svnth6- ysisshows release of H2O al 235oC and of SnCl2at 525'C. 2.8175(50X128), pr6par€spar Howie de l'Universit€ d'Aberdeen' X-ray-precessionpatternlshow that the crystals are rhom- tiquq R,A. prdsententen plaquetteshexagonales minces, bohedral, spacegroup R3m, R3m or R32, and commonly en ilcosse, se uniaxes positives. Cette phase twinned on (ffiI). Guinier-Hiigg powder data were refingd incolores, unir6fringentes, possbde diffraction presque identique iL celui to give hexagonalparameters a 10.0175(3),c 44.014Q\A; un clichd de phasessont dfunorphes,I'abhurite c/a 4.3937. The pri"ncipal lines in the powder-diffraction de I'abhurite. Les deux 6tant rhombo6drique et les cristaux synth€tiques, hexa- pattern [d in A (l)(hkl)l are: 4.139(50)(tl6), gonarD(. 3.634(35X0.l. l 1), 3.404(50)(208),3.27 | (35X2I l), 3.244(35)(122), 3.r42(3s)(2r4), 2.9074(3s)(2r7), par la R€daction) 2.8915(70X300),2.8381(25)(303), 2.8175(50X128), Clraduit 2.53l3(lmxl.l.l5). Syntietic crystalsprepared by Dr. R.A. d'6tain, Arabie Howie of the University of Aberdeen, Scotland are thin, Mots-clds: abhurite, hydroxychlorure colorless, hexagonalplates that show no birefringence, are S6oudite, uniaxial positive and produce an X-ray pattern nearly iden- tical to that of abhurite, The two phasesare dimorphous: abhurite is rhombohedral, the synthetic crystals are hex- agonal. INtnooucloN Keywords: abhtrite, tin chloride hydroxide, Saudi Arabia. Abhurite, a new mineral speciesof composition Sn3O(OH)2C12,was found as a corrosion product on ingots of tin recoveredfrom the cargo of a sunken SoMMAIRE ship, wrecked possibly 100years ago, lying in a cove of the Red Sea known as Sharm Abhur. The site L'abhurite Sn3O(OH)2C12est une nouvelle espdcemin6- (Lat,2l"4'N, Long. 39"07'E) is about 30 km by rale qui se trouve dans des protub6rances en forme air north of Jiddah, Saudi Arabia. The shorelinenear d'ampoulesA la surfacede lingots d'6tain submergdsdepuis the coveis borderedby coral reefs, and the arearecei- environ cent ans d la suite d'un naufrage. Le site de la ves water runoff only intermittently. The tin ingot ddcouverteest ir environ 35 m de profondeur, dans un bras was located inside the cove on a sandy bottom at a 30 km de la Mer Rouge appeld Sharm Abhur, i environ depth of about 35 m in water of about 21'C. en Arabie S€oudite. L'abhurite forme au nord de Jiddah, geographic des cristaux en plaquettes incolores i six c0t6s, minces et An attempt to identify the source of fragiles,d'un diambtremoyen d'environ 1.5mm. Les pla- the ingot was made by comparing trace elements quettes sont unir6fringentes; la figure uniaxe est positive, reported for cassiterite ores and the corresponding et <o6gale 2.06. Nulle fluorescencene fut ddtect6ei aucune smelts(Rapp 1978).The data availableare insuffi- cient for positive identification but, on the basisof *Publication authorizedby the Director, U.S. Geological antimony content, tin ore from Bolivia seemto be Survey, March 16, 1984. a possiblesourc€ for the tin ingot from SaudiArabia. 233 234 THE CANADIAN MINERALOGIST Few descriptions have been made of alteration crusts that contain somewhat less Cl than the ma- products of tin ingots exposedto marine waters for rine sample. Smythe consideredthat the chloride so- long periods. Encrustedtin ingots recoveredfrom lutions were active in an initial electrochemicalreac- a tidal river in the Kampar area, westernMalaysia, tion in the corrosion proce$s.Tin artifacts recovered have been describedby Hosking (1970). In these from the Winnipeg River, Ontario carry incru$tations crusts, investigators at the British Museum (Natur- of the new minerals romarchite SnO (Organ & Man- al History) tentatively identified two phasesof tin darino 1971) and hydroromarchite 3SnO.H2O oxychloride. Hosking suggestedthat the tin oxychlo- (Howie & Moser 1973). ride was formed by reaction with salt accidentally Fragile, colorless crystals of high index of refrac- spilled on the ingot just after it had been poured. tion were found in blisters that formed on the ingot Ariother instanceof saline corrosion was noted by from Saudi Arabia. Semiquantitativespectrographic Smythe (1946). He found that light greyish brown and energy-dispersion analysis (EDX) in the material occurring on a lead-containing tin ingot scanning-electronmicroscope (SEM) showedthat tin recoveredfrom the seaat Falmouth Harbor, U.K., is the only metallisssmpeaenf of the crystals.These containsas much as 1.6 wt.qo Cl. Five other sam- crystals, named abhurite after the locality, and a ples from ingots that had been buried in soil have closely similar syntheticpolymorph, are described Ftc. l. (a) Abhurite crystals within a fractured pod (mm scaleis shown); O) abhurite crystals with massivecream<olored abhurite and black romarchite on outer rim Oar equals I mm). ABHURITE, A NEW TIN HYDROXYCHLORIDE MINERAL 235 in this paper. The name abhurite has been approved by the Commission on New Minerals and Mineral Names, International Mineralogical Association. In- gots b'earingabhurite crystalswill be depositedat the Smithsonian Institution (Natural History Museurh), Washington, D.C., and at the Royal Ontario Museum, Toronto, Ontario. OCcURRENCE AND MINERALOCY The tin ingot on which the abhurite crystals are found is 18 cm long, 9 cm wide at one end and 8 cm at the other, and 3 cm thick. The ingot is prin- cipally tin, alloyed with minor amountsof Cu, Pb, Bi, Zn and Sb. The larger crystals of abhurite form within blisters or pods that contain a viscous mass of liquid and solids. Within a few months after removal from seawater, the blistershad dried out. The fluid has an acidity (pH) of 1, as determined by indicator paper. The pods, which cover all the surfacesof the ingot, rise as much as 7 mm above the ingot surface and penetrate as much as 5 mrir below the surface.Their basedimensions range from about I to 10 mm. Thesepodlike chamberspermit- ted the formation of large, transparent crystals of abhurite (Fig. l). Abhurite crystals that are unprotected by the blisters formed on the surface of the ingot to a depth of about 2 mm, and wereinter- rupted in their developmentby a covering of romar- chite and a subsequenl precipitation (about 2 mm Frc. 2. (a) Abhurite crystalsin multiplelayers, with typi- thick) of kutnohorite, aragoniteand coral. This coat- cal anglesof 120";(b) abhuritecrystal with stepangles ing apparently protected the tin ingot from further of 60'. Bar equalsI mm in both views. reaction with the seawater, and also coatedthe pods. Most of the abhurite contains fragments of the tin alloy and other crystallites. Apparently, not all of Some crystal habits of abhurite are shown in the tin is completely dissolved in the corrosion Figures2 and3a. The hexagonalplates are bounded process,and the remaining fragments were incorpo- by rhombohedral facesthat give poor optical gonio- rated into the abhurite orystalsand masses.The white metric signalsal p - 43". For the negativerhombo- metallic-appearing spherical inclusions have been hedron {0115}, g is equal to 4.6o . Figures2b and identified by X-ray diffraction as B-tin, $imilar to 3a show the common twin habit of abhurite, in which the ingot metal. one individual twinned on (0001) coalesceson the The liquid core containing the abhurite crystals is basal face of the other, felming beveled triangular encasedby a shell of milky white to tan cryptocrystal- elevations. In crossedpolarized light the crystals are line material, which in turn is rimmed by a black to bluish grey to colorlessand show a positive uniaxial bluish black material containing romarchite (Fig. 1b), interference-figure. The physical and chemical and may be followed again on the outer surface by properties of abhurite are summarized in Table 1.