American Mineralogist, Volume63, pages 715-719,1978 Sarabauite,a newoxide sulfide mineral from the Sarabaumine, Sarawak, Malaysia Izum Neret Departmentof Chemisty, The Uniuersityof Tsukuba Sakurq-mura, I baraki 300-3l, Japan Hnrtur AolcHI Nihon Seiko Company,Ltd.,2 Shimomiyahi-cho Shinjuku,Tokyo 162,Japan SerossrMersugenn, AKIne Keto Departmentof Geology,National ScienceMuseum 3-23-l Hyakunin-cho,Shinjuku, Tokyo 160,Japan KezuNosurnMesuroul, TAKASHIFunwlnn KarasumaDemizu Nishiiru, Kamikyo, Kyoto 602,Japan eNn Kozo Ne,cnssIl,ur Depqrtmentof Chemisty, The Uniuersityof Tsukuba Sakura-mura,Ibaraki 300-3I, Japan Abstract Sarabauite,CaSb,oO,oS., is a new mineralfound at the Sarabaumine, about40 km S{ of Kuching, Sarawak,Malaysia. It occurs as small realgar-likemasses in vein-like mineral aggregatescomposed of quartz,calcite, wollastonite, stibnite, and minor senarmontitein an altered limestone.It is probably a product of primary hydrothermalmineralization. The mineralismonoclinic,spacegroupC2/c,a:25.37(2),b=5.654(l),c:16.87(l)A,B= 117.58(4)',and Z : 4. The strongestX-ray powder lines are 3.215(100X514), 2.817(88X020,5r2.-406,800).3.466(78X312),3.182(60)(5il),3.164(s0X802),4.227(42)(ffi2), 2.583(40)(421).It has a realgarJikecarmine-red color, resinousluster, and orangestreak. Cleavageis not observed.Vickers microhardness(20 g load) is 272+6 kg/mm'. Specific gravity is 4.8 (meas.)and 4.99 (calc).Under the ore microscopeit is gray with brownishto purplishpleochroic colors and hasstrong reddish-orange internal reflections. The reflectances are:486 nm, 25.8-20.1percent; 546 nm, 24.7-19.7percent; 589 nm, 23.5-19.1percent;656nm, 20.0-14.0percent for maximaand minimarespectively. Electron microprobe analysis gave Ca 2.43,Sb 74.89,O9.61, S 11.91,total 98.84 percent, corresponding to Ca".rrSbroOr.r.Su.o..It is readily soluble in conc. HCI with evolution of HrS and slowly in conc. NaOH and dilute HNO, solutions.Single crystals of sarabauitewere synthesizedunder hydrothermalcondi- tions: 500oC,1000 kglcm'?. Introduction is the second naturally occurring oxide sulfide min- A realgar-like carmine-red mineral was found in eral, kermesite (SbrSrO) being the first. hydrothermal ore deposits of the Sarabau mine, Sara- The mineral is named sarabauite after the locality. wak, Malaysia. After microprobe analysis and syn- The mineral and the name have been approved by the thetic work, the mineral proved to be a new species Commission on New Minerals and Mineral Names, having the ideal chemicalformula CaSb'oO'.S..This IMA. ow3-N4X/78/0708-0715$02.09 715 7t6 NAKAI ET AL: SARABAUITE, A NEW MINERAL age.The habit is tabular and prismaticparallel to the 6 axis.The specificgravity measuredby Bermanbal- anceis 4.8, while the calculatedvalue from the theo- retical formula is 4.99. Vickers microhardnessis 272+6kg/mm2 (load 20 g). Themineral is not brittle but is to someextent sectile. Under the ore microscopeit is gray-whitewith discerniblereflection pleochroism changing from a brownish to a purplish tint. Internal reflectionsare quite remarkablewith reddish-orangecolor. No po- lishingcleavage is observed.The reflectancesare:486 nm,25.8-20.1percent; 546 nm, 24.7-19.7percent; 589nm, 23.5-19.1percent; SARABAUMINE 656nm, 20.0-14.0percent J/ for maxima and minima respectively.These figures 20 kn '/ may be affecteddue to internal reflections. Owing to its extremelystrong absorption, very lim- Fig. l. Locationmap of theSarabau mine, Sarawak, Malaysia. ited optical propertiesfor transmittedlight wereob- tained. Description The samplesused were synthetic CaSbroO,oS.. It is opticallybiaxial negative with 2V about90o, | : The ore depositsof Sarabaumine are located near Y, and the pleochroismis from reddish-yellow(lly) Bau,about 40 km SW of Kuching,Sarawak (Fig. I ), to brownish-red (llZ'). where limestone,shale, chert, sandstone.and con- glomeratebelonging to the Bau Seriesof Upper Ju- X-ray crystallography rassicto Cretaceousare exposed.They are locally The precessionand Weissenbergphotographic intruded by microdiorite,microtonalite, dacite, and studiesshowed the mineral to be monoclinicwith quartz-andesite of late Tertiaryage, and the volcanic possiblespace group either Cc or C2/c. The latter is activity is consideredto be responsiblefor the miner- preferredaccording to the resultsof a structuralanal- alization gold, of silver, antimony, and mercury ysis (Nakai et al., 1977).The unit-cell parameters foundin the rocksof the BauSeries (Wilford, 1955); refined with a four-circle automatic diffractometer very probably the formation of the Sarabaudeposits (MoKa, = 0.7092584)arca = 25.37(2),b=5.654(l), was due to the samegeologic event. c = 16.87(l),4'and p : 117.58(4)". Only one specimen showing the mode of occur- In the sarabauitestructure (Nakai et al., 1977),the renceof sarabauitewas found. All descriptionsand studieswere made on this material. It is a pieceof gray fine-grainedlimestone cut by a sarabauite-bear- ing vein-likebody more than 5 cm in width. The modeofoccurrences ofsarabauite and the associated mineralsincluding stibnite, wollastonite, quartz, cal- cite,and minor senarmontiteare depicted in Figure2. Sarabauiteforms long tabular crystalselongated along the b axis, and the maximum lengthreaches I mm. A well-developedexternal shape was only occa- sionallyobserved under the oremicroscope; however, evenso, the morphologycould not be determined. The closeassociation of stibnite,senarmontite, and sarabauitesuggests the absenceof any stablephases with intermediatecompositions between CaSb,oO,o S.-SbrSB-SbrOsunder the conditions of sarabauite formation, which excludedthe formation of kerme- site. Physicaland optical properties Fig. 2. Sketchof the studiedsarabauite-bearing Sarabauitehas a realgar-like specimen.Sa: carmine-redcolor. sarabauite;Sb: stibnite(with minor senarmontite):Wo: wollasto- resinousluster, orangestreak, and no visible cleav- nite; Ct: calcite. NAKAI ET AL: SARABAUITE, A NEW MINERAL 717 Sb atomsare coordinated by threeO and/or S atoms this givesa certaindifference between the two struc- to form trigonalpyramids of SbO3,SbSg and SbSrO. tures.The kermesitestructure (Kup6ik' 1967)has a The SbOg pyramids compose4-membered and 8- similar network composedof Sb, S, and O atoms memberedSb-O rings.These two rings link by shar- parallelto (100).As mentionedabove, in sarabauite ing a cornerO atom to form a chainparallel to [001]. the netsare linked by the Ca atomsto form a three- On the other hand,two SbS3and two SbSrOpyra- dimensionalstructure, whereas in kermesitethe nets mids form an 8-memberedSb-S ring. Moreover the are stackedin the a axisdirection and linked by weak 8-memberedSb-O and Sb-S ringslink by sharinga Sb-S and Sb-O bonds.The averagebond distances cornerO atomto form a chainparallel to [101].As a are:Ca-O 2.467,9b-O2.000 and Sb-S 2.4654. Simi- whole, thoselinkages of ring structuresgive rise to a lar valuesare observed in kermesiteas well asin other two-dimensionalnetwork parallelto (010).The Ca oxidesand sulfides. atom is sandwichedbetween the two 8-membered The X-ray powderpattern obtained by the diffrac- Sb-O ringsand formsa CaOepolyhedron. Thus the tometer method using Ni-filtered Cu radiation is Ca atomslink the networksin the b-axisdirection. givenin Tablel. The indexingwas made on thebasis Kermesite(SbrSrO) is the only mineralwhich is of single-crystaldata. There is good agreementbe- compositionallyrelated to sarabauite.However, ker- tween intensitiesof the X-ray powder and single- mesitecontains no cationother than antimony,and crvstaldata. Table l. X-ray powder diffraction data for sarabauite* d obs l/lo hkl d calc d obs Ll Lo d calc 15 200 II.24 1r.33 20 10.0.2 r.922 r.922 r.890 22 202 8.224 6.4t0 6 825 1.888 1II 4.970 4.979 o I0.2.3 1.888 1,859 L.872 18b 5La 4 .452 4.462 36 026 602 4.227 42 623 r.859 II3 3.915 3.924 30 804 1. 859 15b 5L2 3.751 3.748 15 lI8 l. 834 r.830 600 3.748 oz I L .6Z0 7 004 3.738 L32 1.80s 1. 808 rJ . r. o I.79]- T.79L t2 JLZ 3.45r J. {OO 78 r.783 13 314 3.379 3.385 10 r33 1.780 5r4 3 -207 3.215 100 lro r. /lo r.756 TD 5tr 3.L79 3.L82 60 3L7 1.751 8 802 3.155 3. r64 50 oz+ 1.730 1.731 I8 712 3.0s0 3.052 6 531 L.692 L .694 L.673 ID 7].3 J.UU / 3.OII 5 12.2.5 r.o/l 1.672 I LL 2.970 2.970 5 732 020 2.827 2.8L7 88 823 r.o/r 2.816 733 r.655 r.ooo f, )La 2 406 2.8rf 734 1.538 1.640 8 800 2. 81r 10.0.4 L.623 L.620 9 22r 2.752 2-753 zv 5. 1. t0 r.501 1.503 t. )6u 8b zuo 2.7L3 z. tL6 z6 318 r.578 r.)/6 tL) 2.639 2.544 9 1. 571 5b 404 2 .606 2 .607 t8 , f o L.5TZ 2.580 2.583 40 l( I 7 1.569 11 r0.0. 4 2.507 2.503 I4 L>.L.2 1.559 1.550 2.498 15 935 a.)zo I.524 ID 006 2.492 IL / ro 2 .40L 2.409 LU.2-9 I.5L2 1.515 1.483 r.483 I 9r5 2.50L 2 .365 9 13.1. t0 o a't ) 2.327 2.329 5 f,ld L.448 1.450 910 2.285 2.28L 20 I.+5J L .432 J 10.0.0 2.249 2.251 5 04r r.407 L. 407 5D 4b 604 2.188 2.r87 4b* * 44L r.379 1.379 7r7 2-L70 4b L.377 9 6Za Z.LUO 2. r08 16 1.34r L.342 vz) 2.054 2.058 29 542 1. 340 1.328 2 fi.