Canadian Mineralogist Yol.24, pp. 5l-54 (1986)
RAPIDCREEKITE, A NEW HYDRATEDCALCIUM SULFATE-CARBONATE FROM THE RAPID CREEKAREA, YUKON TERRITORY ANDREWC. ROBERTS,H. GARY ANSELL ANDIAN R. JONASSON GeologicalSurveyof Canada,601Booth Street,Ottowa,OntarioKIA 0E8 JOEL D. GRICE Mineral Sciences Division,NationalMuseumof Natural Sciences, 1026MerivaleRoad, Ottawa,OntarioKiA 0M8 ROBERT A. RAMIK Departmentof Mineralogltand Geologlt,Royal OntarioMuseum,100Queen'sPark, Toronto, OntarioMSS2C6 ABSTRAcT
un bon clivage{100} et un clivageparcreekiteprdsente et2.239(calfait {010}.Sadensit€ estde2.2l(l) (mesur6e) sousl'ultraviolet.Elleest cul6e);ellen'estpasfluorescente positive, biaxiale a 1.516(1), B 1.518(l),7 1.531(l),2V" (mesur6) 43" ; l'orientationdeI'indi45(3)",2Vr(calcul6) catriceest:X = c, Y= a, Z = b. Leshuit raieslesplusintensesdg diagrammede poudreobtenupar diffractionX [d en A(t)(afDl sont les suivantes:7.78(100)(200), I ), 3.I I (80)(421,40q, r 1,400,23 4.3| Q0)Q2r),3.88(70X3 6r), 2.s55(s0)(r42,322) eI 2.9t7(50)(43 t), 2.797(60',)(r i la microsonde 082).Lesanalyses 1.899(50)(303,580,233, * analyse des thermogravim€trique et I'analyse 6lectronique gaz6misCIGA-EGA)donnent:CaO36.3,SO326.1'CO2 (enpoids).Le nomrap14.0et H2O23.6,total 100.090 pelleI'endroitoir la nouvelleespdce a 6t6trouv6e.
Rapidcreekite,ideally Ca2(SO/(COr1.4gr6, is a new secondarymineral speciesfrom the Rapid Creek area, northe.rnYukon Territory. It occurson beddingplanesand joint surfacesof a quartz-rich iron formation, as crystalline coatingsand spraysof white to colorlessacicular crystals. The symmetry is orthorhombic, space gogp Pcnb, with a 15.49(l), , 19.18(l), c 6.157(4)A, a:b:c 0.808:1:0.321,Z = 8. Individual crystalshavea maximum len&h of 2 mm and are elongate[001], with forms {010} broad and {100}, {001} minor. The streakis white; lustre vitreous; brittle, fracture splintery; Mohs hardness 2; cleavage{010} perfectand { 100} good; D(meas.)2.21(l), D(calc.) 2.239g/cms; nonfluorescentin ultraviolet light. Rapidcreekite is biaxialpositive,cr 1.516(l),0 1.518(l),r sulfate min6rale,rapidcreekite, 1.531(l), 2Z* (meas.)45Qr',2Zxk*.lc.) 4", indicatrix Mots-clds: nouvelleespbce Yukon,Rapid orientation X = c, Y=a, Z=b. The strongeliteight lines et carbonate de calciumtetrahydrate, chimique. de rayonsX, composition in the X-ray powder-diffraction pattern [d in A(I) (hkl)] are Creek,donndes 7.78(100x200), 4.3r(70)Q2r), 3.88(70X3 l 1,400,23 l), 3. l I (80X421,002), 2.9r7(s0)(43r), 2.797(60)(l61), INtnooucrtoN 2.555(s0)(142,322)and 1.899(50)(303,580,233,082). Microprobeanalysesand TGA-EGA gaveCaO 36.3, SO3 The Rapid Creek - Big Fish River area of the 26.1,CO214.0and }J2O23.6,sum
[email protected] wt.Vo.The name refers to the general locality. northern Yukon Territory is best knpwn for the Keywords: new mineral species,rapidcreekite,calcium sulfate carbonatetetrahydrate,Yukon, Rapid Creek, Xray data, chemicalcomposition. SOMMAIRE La rapidcreekite, dont la formule iddale est Ca2(SOa) (CO3).4H2O,estune nouvelleespbcemin6ralesecondaire d6couvertedansla r€gion du ruisseauRapid, dansle Nord du Yukon. On la trouve sur les plans de stratification et de s€parationd'une formation de fer riche en quartz, sous forme d'enduits ou de gerbesde cristaux aciculairesblancs ou incolores. La symdtrieestorthorhombique, grolrpe spatiaTPcnb, a 15.49(1),, 19.18(1),c 6.157(4)A, a:b:c 0.808:l:0,321,Z: 8. Lesmonocristaux ont, tout au plus, 2 mm de longueur et sont allongds[001], la forme {010} estlargeet lesformes{l@} et {001} sont eftoites.Cescristaux sont fragiles, d trait blanc, 6clat vitreux et cassure esquilleuse;de duretd 2 sur l'4chellede Mohs. La rapid-
unique assemblages of phosphatemineralsthat occur in a sequenceof Lower Cretaceous(Albian) ironstones and shales. However, recent surfaceweatheringhas resultedin the formation of many secondarysulfate and carbonateminerals,most of which havenot beenreportedto date. Among these are aragonite,nesquehonite,dypingite, hydromagnesite, gypsum, hexahydrite, halotrichite, epsomite, jarosite, natrojarosite and diadochite (a sulfatephosphate). Rapidcreekite,ideally Car(SOn)(CO).4HrO,is a new mineral speciesfirst encounteredin 1983,and to date found only at one locality along the valley of a tributary (unofficially, CrosscutCreek)of Rapid creek, at latitude 68"33'45',N, longitude 136"47'30'W. Rapidcreekiteoccursas a secondary phaseon dilated joint-surfacesand beddingplanes in a blocky, quafiz-rich bed in the sideritic ironformation. Minor amounts of glpsum and aragonite
51
52
THE CANADIAN MINERALOGIST
are associatedwith rapidcreekite,and kulanite is slowly in heavyliquids, a measureddensityof 2.21(l) g,/cm3was obtained, in reasonableagreementwith found on the holotype specimen. The mineral is namedfor the generallocality; both the calculated density of 2.239 g/cm3 for nameand mineral havebeenapprovedby the Com- CalSo)(Co)4}J2o. rnission on New Minerals and Mineral Names, Optical measurementswere made on a spindle I.M.A. The holotype specimen,consistingof a few stageusing sodium light O 589 nm). Rapidcreekite grams of material on matrix, is housedin the Sys- is biaxial positive, cu 1.516(l), 0 1.518(l) and y tematic ReferenceSeriesof the National Mineral Col1.531(1).The measured2V*is 45(3)",closeto the lection, at the GeologicalSurveyof Canada,Ottawa, calculatedvalue of 43" . Optical orientation is X: c, under cataloguenumber U346. Addiiional speci- Y:a and Z:b. mens of rapidcreekite are preservedat the GeologiCRYSTALLOGRAFHY cal Survey and at the Mineral SciencesDivision, National Museum of Natural Sciences,Ottawa. Precessionsingle-crystalstudies employing Mo radiation of two crystalfibres showthat rapidcreekite Pnvsrcal ANDOPTICALPRoPERTIES is orthorhombic, spacegrovp Pcnb, with measurgd Rapidcreekiteoccursmost commonly as radiat- unit-cellparametersa I 5.45, b 19.16and c 6. I 65 A. ing spraysof white to colorlessacicularcrystals,in The levels collected are hle0-hk2, 0kl-Skl and both isolatedclustersand pervasivecoatingson rusty- h\l-h\l. The X-ray powder-diffraction data (Table l) were^refinedon l8 reflectionsbetween3.005and weathering quartz-rich iron formation. Individual crystalsare colorless,transparentand acicular, elon- 1.655A for which unambiguousindexing was posgate parallel to [001], with forms {010}broad and sible, basedon precessionsingle-crystalfilms. The tl00l, [001]minor (Fig. 1), and approach2 mm in refined unit-cell par4meters arei q 15.49(l), b maximum length. The coarsermaterial has a length- 19.18(l), c 6.151(4)A, V tgZg.Z 43, and q:b:c to-width ratio of about 50:1. Bundlesof individual 0.808:I :0.321. The strongestdiffraction-lines are crystals appear lath-shaped. The mineral is brittle closeto thoseof gypsum,but the completepowderwith a white streak, vitreous lustre, splintery frac- pattern is significantly different from any mineral ture, and a Mohs hardnessof 2. Observedcleavages ofthe gypsumgroup. However, the powder data are are [010] perfect and {100} good. Rapidcreekiteis very similar to the
[email protected]. nonfluorescentunder both long- and short-wave 29-294) described by Walenta (1972) from the ultraviolet radiation. Although the mineral dissolves Johann mine, Wittichen region, Germany. There seems little doubt that this latter mineral is the arsenateanalogueof rapidcreekite.This is further supported by the near-identity of their optical properties. TABLE I. X.RAY POVDER-DTFFRACTION DATA FOR RAPIDCRBEKITE r*
Ftc. l. Scanning-electronphotomicrograph of rapidcreekiteshowingtypical habit of crystals.Lenglh of bar is l0 rn..
a,i .*.
100 20 J l0 70
7.7t 5.tt9 4.91 4.6t s.3l
70
3.88
40
).66
40
3.41
2b
3.72
t0
,.ll
20 50
1.005 2.917
1('b
2.871
60
2.797
1@
2.743
30
2.61
50
2.555
20
2.tt49
10b
2.)a6
a,i."t". 7.75 ,.48 tt.9l 4.67 4.3t 3.tt t.a7 ,.85 3.64 3.66 3,40 t.23 3.20 ).10 ,.a| 3.0t2 2.917 2.t80 2.a61 2.79t 2.754 2.730 2.659 2.555 2,549 2.444 2.398 2,t91 2.370
114.6 mm Debyq.Scher.s Fsds 7tA), b=br€d llne ocukGl.r4l
hkl 200 ln l2l 2ll Z2l 3lt r.00 231 l4l 321 24r 4ll 060 421 0m 251 431 122 2C2 l5l 351 l?2 52r 142 122 t32 080 4t2 lto
oA .*.
td
2.3t2 30 5 t0 20
2.r7t 2.@l 2.q70
10
2.*4
5 40 40
2.0@ 1.986 1.9'
50
t'6"
l0 5
L.E3t 1.786
l0
t.76t t.7t0 l.68rr t,655
@msa, Cu radatlon Ni tllt€
irde:cd eith o 15.49.b l9.IE sd c 6.lr7i
oi *t". 2.t16 2.211 2.245 2.2ta 2.212 2,170 2.6t 2.071 2.Ot7 2,019 2.035 2.010 l.9tt 1.949 1.907 1,E96 1.89i 1.a92 l.a, 1.7a7 1.766 1.75a 1.757 l.7ll L6Ei 1.656
hk'l 342 371 t'l 2 l8l 5t2 561 7ll 072 4t0 r03 740 5tt2 Dr 303 '80 zrt @2 243 491 722 652 6t0 503 742 4l!l
RAPIDCREEKITE, A CALCIUM SULFATE-CARBONATE
FROM RAPID CREEK
2000
1000
53
too c
80 .9 (tt .9 E
;60
c qt
1E - ' 4 0 o
bzo
o-
4000
15 0 0
500
W a v e n u m b e rc m - r Ftc. 2. Infrared-absorptionspectrumfor rapidcreekite.
CHEMISTRY
Rapidcreekite was analyzed by means of a Materials Analysis Company (MAC) electron microprobe equipped with a KEVEX energydispersion spectrometer (M. Bonardi, analyst). Accelerating voltage was 20 kV with a sample current of l0 nA as measured on kaersutite. To minimize sample degradation and compositional changedueto electronbombardment,a slightly defocusedbeam was used over a counting time of 100 seconds. An energy-dispersionscrmon a hand-picked crystal aggregateindicated that Ca and S are the only elementspresent with atomic number gleater than 10. Subsequentenergy-dispersion analysesweremade usinggypsum(NMC 17182,Moose River, Ontario) as a standard. Analytical data were corrected with EDDI, an in-houseenergy-dispersiondata-reduction program written by G.J. Pringle. TGA-EGA @volved Gas Analysis) determinationsfor H2O and CO2 were made on 3.605 mg of sampleusing the Mettler thermal analyzer and integrated massspectrometerat the Royal Ontario Museum.Major peaksat 230",660" and 1105'Careascribedto the evolution of H2O, CO2 and SO3,respectively. A 25 mg sampleof rapidcreekitewas checkedfor the presenceof other anions using a Dionex anion chromatograph. Results of one analysiswere: F0.09,Cl- 0.03,PO4r 0.07and NO3-0.15weightgo, most likely attributable to contamination. CombinedanalyticalresultsgaveCaO 36.3, SO3 26.1, CO2 14.0 and Il2O 23.6, total 100.00weight 90. Assuming S= I , the empirical formula for rapidcreekite is Ca,.er(SO)r.00(COJo.e8.4.02H2O or,
ideally, Caz(SO+XCO).4HzOwith Z=8. The mineral dissolvesslowly in 1090HCI with slight effervescence. Calculationsusing the Gladstone-Dalerelationship yieldedKc = 0.232and Kr : 0.233for constants reported by Mandarino (1981); hence l-(Kp,/Kd is 0.0043,indicating superior compatibility (Mandarino 1979). An infrared-absorption analysis@ig. 2) indicates that the formula CaISO)(CO3).4H2O is to be preferred over Ca2(SO)(HCO3XOH).3H2O.No positive evidencewas found for the presenceof HCO3- or OH- in rapidcreekite.However, a crystalstructure determinationwould be necessaryto verify the correct formula. AcrNowrsncEMENTS The authors thank J.L. Jambor, CANMET, for the determination of the specific gravity, V.H.E. Rolko, CANMET, for the infrared-absorption study, D.A. Walker, G.S.C., for the SEM photomicrograph,M. Bonardi, G.S.C., for the electronmicroprobedata, W.G. Young, G.S.C., for drafting Figure 2, A.I. Maclaurin for Dionex analyses and G.W. Robinson, N.M.C., for helpful discussions. Logistical support in the field was supplied, in part, ty the Polar Continental Shelf Project @nergy,Mines and Resources,Canada)and by the Inuvik ScientificResourceCentre(Indian and Northern Affairs), whose assistance is gratefully acknowledged.We thank PeteJ. Dunn, EugeneE. Foord, Antlony R. Kampf and Robert F. Martin for critical readings of the manuscript.
THECANADIANMINERALOGIST
54
WALE*re, K. (1972):The secondaryminerals of the Co-Ni-Ag-Bi-U oreveinsin theWittichenregion, 23,279'329 (ia (1979): relaThe Gladstone-Dale Meroanno, J.A. I:ntral Black Fotest. Aufschluss German)' tionship. III. iome'general applications.Can. Mineral.17.71-76, RsFERENcss
(1981):The Gladstone-Dalerelationship.IV. fne iompitiUility conceptand its applicatioi. Can. Minerql. 19, M1450.
ReceivedJune 27, 1985,revisedmanusoipt accepted September4' 1985.
