THn AUERICAN MtxERALocIST

JOURNAL OF THE MINERALOGICAL SOCIETY OF AMERICA

Vol. 55 SEPTEMBER-OCTOBER Nos. 9 and 10

DYPINGITE, A NEW HYDROUS BASIC CARBONATE OF , FROM NORWAY GuNNan sk M us eurn' " ?)ili;,f,#r: ;r;:: fr:i;:i

ABsrRAcr

The new mineral dypingite was found in the Dypingdal serpentine- deposit, Snarum, South Norway, where it occurs as a thin cover on serpentine. ft is of late secondary origin, deposited from cold, leaching solutions. Chemical analysis of 100 mg of handpicked material yielded the formula SMgO.4COz.6HgO or Mgs(COa)r(OH)r'5HzO. By heating at 150oC,dypingite is converted to hydromagnesite,5MgO'4COs'5HsO or Mgr(COs){(OH), '4H'O' Dypingite forms white globular aggregates, averaging 0.3 mm, with radiating structure. It has a pearly and is both fluorescent (light blue) and phosphorescent (yellow-green). Refractive indices are a:1.508,9:1.510, r:1.516 and the calculated specific gravity (Gladstone and DaIe formula) is 2.15. The strongest reflections on X-ray powder diagrams are (in A): 10.6 (100), 5.86 (90),6.34 (60), 2.53 (50), 2.17 (50). rnfrared absorption spec- trum and DTA curve are very similar to those of hydromagnesite' X-ray powder data are also given for giorgiosite, an imperfectly known basic mag- nesium carbonate from Santorin. Strongest reflections (A) : 3.40 (100), 3.29 (70), 2.92 (ffi), 4.M(n),3.e7 (40), 2.46 (4O). fr.rrnooucrroN Serpentinespecimens covered with a white surfacealteration product, in appearance very much resembling hydromagnesite, were collected by the author in 1961from the serpentine-magnesitedeposit at Dyping- dal, Snarum, South Norway. Optical spectrography showed large amounts of Mg, only very minor amounts of Fe, Ca, Al, Si (probably due to admixture of serpentine),and traces of Mn, Ti, B. Microchemical tests showed the presenceof Mg and COz. The X-ray powder pattern was not identical with hydromagnesite or any other known magnesium . A detailed examination showed the substance to be a new mineral, closely related to hydro- 'dip-ing-ite) magnesite. The name dypingite (pronounced is for the locality. The mineral and name were approved in advance of publication by the Commission on New Minerals and Mineral Names, I.M.A. Type material is preserved at the Mineralogical-Geological Museum, Uni- versity of Oslo, Norway. r457 1458 GUNNAR RAADE

OccunnBNcB Small serpentine-magnesitebodies occur in the Precambrianrocks of Snarum west of the Oslo Region.These form steeplvdipping, elongated iensesup to about 100 m long and 15 m wide. The wall rocks are an- thophyllite-bearingquar tzite, amphibolite,and breccia. The Dypingdal deposit was formerly worked for magnesite and serpentine,today the rock is used for ornamental purposes.Several interesting minerals are found here, e.g.serpentine pseudomorphs after forsterite, hydrotalcite/manasseite,szaibelyite, crystals, etc. (Jcisang,1960 and 1966).

Pnysrcar PnopnnrrBs Dypingite forms white globular aggregatesoften showing radiating structure, occurring as a thin cover on serpentineor more rarely on hydrotalcite. Larger aggregateshave a pearly luster. It is easily dis- solved in cold dilute hydrochloric acid with effervescence. The mineral showsa light blue fluorescencein ultraviolet light, both long-waveand short-wave,and a yellow-greenphosphorescence, giving best responseto middle-waveradiation. Exact optical measurementswere not possibledue to the fine-grained nature of the mineral (averagethickness of fibers1pm). It is colourlessin transmitted light, locally pigmented. Radiating aggregatesconsist of fi.berswith*elongation. The fibers seemto be elongatedparallel to the I/ axis.a:1.508, g:1.510, 7:1.516. ft was not possibleto determinehardness or specificgravity. From the rule of Gladstoneand Dale the specificgravity is calculatedto 2.lS (k valuesfrom Larsen and Berman. 1934).

X-Rev Powppn Dere The powder data are given in Table 1. The mineral is finely crystaliine and always gives somewhat diffuse reflections.The pattern slightly re- semblesthat of hydromagnesitewith regard to the inner lines, but is clearly different (compare Fig. 1). Attempts at indexing the pattern were not successful.The material is unfortunately not suited for single crystal work. Dypingite may be monoclinic (as is hydromagnesite).

f NrnA.nnoAesoRprrow ANar,ysrs The infrared spectra of dypingite and hydromagnesiteare shown in Figure 2. The hydromagnesitecurve is virtually identical with that pub- lishedby Mumpton etol. (1965).The two spectraare remarkably similar, suggesting a close structural relationship between these minerals. DYPINGITT' 1459

Tasr-n 1. X Rev Pownnn Da.ra ron DvprNcrrn

I/Ioest d iA.robs I/Ioes| d 141obs. IfloesL. d 1A)obs.

30 40 316 50 2.17 100 106 40 307 5 L.L] 10 7.89 5 2.96 5 209

10 /.J/ 40 293 20 2.02 60 6.34 30 284 10 t.99 90 586 20 2.81 10 1.96 5 552 20 2.78 5 1.92 20 4.45 50 2,53 5 1.90 30 4.20 5 250 5 t.73 10 4.10 10 2.11 5 1.68 10 3.90 5 2.36 5 166 10 3.68 234 5 t.64 10 3.+9 20 225 5 1.61 ',21 10 3.33 20 2 5 |.52

Guinier quadruple focusing camera) efiective diameter 22.9 cm, Ire radiation, Mn filter Internal standard: lead nitrate.

Absorption bands resulting from OH- groups (3650 cm 1) and water of crystallization(3510 and 3450 cm-1) are identical for both, as are COs2- stretchingbands (1480, 1420,1120cm-I) and COa2-bending bands (880, 850,800 cm-1).Two small absorptionbands at 1020and 940 cm-l seem to be characteristicfor dypingite.

d (i)

r08 6 51 1q

Dypingite

Hydromognesi te

Frc. 1. Diagrammatic representation of dypingite and hydromagnesite powder pal- terns, constructed for 9 cm Debye Scherrer lilms and Ire radiation. Powder data for hy- dromagnesite from Murdoch (1954) Vertical scale indicates the relative intensities of the reflections. 1460 GANNAR RAADE

a 1 I E E o t) -o o o o rt rr) o o o \C o o o N v Nc0 o E m o ro o n ocl (! o ol o s Yai o o ol N - o o'F o o,i rt 'og (oH !w, o o .2': o O 'PP @ 6ltr

o o Yi6 o o|O o .Yh I o '6x o) o o p'; o oF0? So E Fi,

o o .q9 L __ o o 'd€ sF sdx

o o t:F o -'-/ o c'! @ (o .5 @ o o a.-q ,/ o O >\9 I @ .:!r" o o sd? o n; 3a o 9.1 ol 6t xo

d92

63 o o _8.4 o Ocd \ Od o od G

N o9 ro - o|r) oE ol o 3ci Y o ooo o \l o @@v N E3 3 e Ro

(%) 33NVrilr{SNVUI (%) 3 JN VrilFtS NVUI DYPINGITE 1461

5050c

,'t;oooc oC o 370 510oC 5050c

2650C 12000c 1250c Dypingite 550c

5100c 3750c 2650c

12000c 0c 60 Hydro m og n esite

Frc.3 D l'A curveso[ dypingiteand hydromagnesite. Rate of heating10 deg/min; thermocouplePt/Pt+l3Ta lth; referencejunction OoC1 reference material AlrOa.

DrrrBnnNrrAr, THERMALANar-ysrs Samples oi dypingite (5.6 mg) and h1'dromagnesite(6.3 mg) were heated in air at one atmosphere from room temperature to 1200oC (Fig. 3). Hydromagnesiteshows four endothermicpeaks: a very small oneat 60oC(hygroscopic water) and three major onesat 265,375,510"C (water of crystallization,OH groups,COz).An exothermicpeak at 5050C is prominent (crystallization of cubic MgO). It should be noted that this DTA curve, which was obtained with a very sensitive apparatus (Du Pont 900 thermal analyzer), is rather different from those published previously(Beck, 1950.Hsiu-Chang and Hsieh-Yen,1965). At temperaturesabove 125oCdypingite gives a DTA curve nearly identical with that of hydromagnesite. ilhe exothermic peak and the major endothermicpeaks are the same (except that the 375oCpeak is more flattened). At lower temperatures,however, dypingite shows two pronouncedendothermic peaks at 55 and I25oC. 1462 GUNNAR RAAD]L

t0

^8 o ,3 E o Et o o f 3 o o ,og

r00 200 300 100 500 600 700 800 900 "c

Frc. 4. Thermogravimetric curve of dypingite. Rate of heating 10 deg/min.

TnBnuo cnLvrMETRrcANer,vsrs Heating of dypingite in air at one atmosphereproduces the thermo- gravimetric curve shown in Figure 4. The total weight loss is 55.7 per- cent; 3.5 percent is lost below 125"C (small amounts of serpentinewere presentin the sample).The end product is MgO (periclase),as shown by X-ray examination.

Teer-r 2. Cnpurcar, ANelvsrs ol Dvptnctrn

Analyst: John Marinenko

(1) (2) (4)

Mso 38.3 39.4 4.60 5 41.5 CaO <0.2 Total iron as FezOr 02 COz 36.3 37.3 4.00 4 36.2 Total HrO 22.7 ??? o. rt o 22.3 Acid insoluble 2.0

99.5 100.0

Loss on ignition 58.8

(1) Figures in weight percent. Magnesium was determined volumetrically with EDTA; calcium by atomic absorption; total iron by o-phenantroline spectrophotometric pro- cedure; COz and total HzO gravimetrically in a semimicro train. Acid insoluble means insoluble in hot dilute HCI. (2) Recalculation to 100 percent, omitting minor constituents. (3) Mole proportions. (4) Theoretical composition for 5MgO. 4CO z' 6HzO. DYPINGITE 1163

CnBlrrc.q.r,ColrposrrroN 100 mg were carefully handpicked and purified for chemicalanalysis under the binocula,rmicroscope. Small amounts of serpentineand possi- bly hydrotalcite and magnesitewere present as impurities in the final product. The result of the analysisis given in Table 2. The mole propor- tions are rather closeto 5MgO'4CO2.6H2O.Hydromagnesite has the composition 5MgO'4COr.5HrO. (Some authors still quote the form- ula as 4MgO.3CO2.4HrO, although the evidence of Fenoglio (1936) in support of the 5:4:5 ratio was fairly conclusive). According to this analysis, dypingite is a mineral very near to hydro- magnesitein chemical composition,containing just one extra molecule of water. This is supportedb1' all the data presented:1) the DTA curves are nearlv identical, but show that dypingite contains some loosely bound water which is lost at comperativell'Iow temperaturesl2) thermo- gravimetric analysisindicates a weight loss of 3.5 percent below 125oC; the theoretical value for loss of one mole of water from SMgO.4COz .6HrO is 3.7 percent; 3) the infrared spectra are nearly identical; 4) although the X-ray powder patterns are clearly different, they do show somesimilarities. The final proof is renderedby the fact that when dypingite is heatedat 150oCfor severalhours, it is completelyconverted into hydromagnesite,as shown by X-ray analyses.The X-ray diagram of the heated dypingite is in every detail identical with hydromagnesite.

DrscussroN The compounds5MgO.4COz.5H2O and 5MgO.4COz.6HzOwere syn- thesizedby Menzel and Briickner (1930). They report that the X-ray

Brucite Mognesite

Hydromognesite Dypingite o Artinit " . crringtonite Nesquehonite Lonsfordite

Hzo Cot

Frc. 5. Part of the system MgO-COz H:O. NIineral formulas are plotted in mole percent. Barringtonite, MgCO3.2HzO, was described by Nashar (196.5). t464 GUNNAR RAADE

T.q.no 3. X-Rev Pownnt Dern lon Groncrosrrn

I/Isest. d (A) obs. I /In esI d (A) obs. I/Irest. d (A) obs.

10 7.8r 100 3.40 20 2.26 10 6.82 70 3.29 20 2.19 30 5.80 60 2.92 20 2.rl 30 10 2.70 20 1.98 40 4,M 30 2.62 10 r.94 30 4.t4 30 2.56 10 1.88 40 3.97 10 2.49 20 1.84 10 3.72 +0 2.46 10 1.81 20 J.JI 10 2.29

9 cm Debye-Scherrer camera, Fe radiation, Mn filter. spectra of the two substancesare identical. I{owever, their pictures only show a few, broad lines. In fact, it is possibleto tell them apart by con- sidering spacing differences. Dypingite is of recent formation in the Dypingdal deposit, since it occurs as a weathering product on material in the dumps. It is probably deposited from cold, leaching solutions during wintertime' (For a dis- cussionof the stability of carbonatesin the system MgO - COz- HrO, see Langmuir, 1965). CoNcr-usroN The following basic magnesium carbonatesare now known in nature: artinite, Mer[(oH)rl COr].3Hso; hydromagnesite, Mg6[oHl (COr)rJt .4H2o; and dlpingite, Mg6[oHl (co')r]r'5Hzo (Fig. 5). Giorgiosite is a very poorly described basic from the Santorin islands (Lacroix, 1905). Caillbre (1943) reported that the X-ray spectrum and DTA curve are not identical with hydromagnes- ite. This is supported by -y own investigations on material from the original locality. Since the X-ray powder data were never published, they are given here in Table 3. A number of basic magnesium carbonates are describedin the chemi- cal literature. As X-ray data are almost invariably lacking, most of these are extremely suspect. Giorgiosite is not identical with the compound 4MgO.3CO2.3H2O,described by Walter-L6vy (1937), and for which proper X-ray data are given.

Acrxowr.nooerdrNrs I would like to thank people at the following institutions for valuable assistance: Mineralogisk-Geologisk Museum, Universitetet i Oslo (X-ray work, optical determina- tions); Institutt for Geologi, Universitetet i Oslo (optical spectrography, DTA); Kjemisk DYPINGITE 1465

Institutt, Universitetet i OsIo (infrared absorption analysis); MineralogischesInstitut, tlniversitiit Kiel (thermogravimetricanalysis). Special thanks are extended to J. Marinenko of U. S. GeologicalSurvey, Washington, D. C., for the chemicalanalysis. A sample of giorgiositewas receivedfrom S. Cailldre of Mus6um National d'Histoire Naturelle, Paris. ProfessorsK. S. Heier and H. Neumannkindly read the manuscript.The English text was corrected by B. Jensen. RBrrnoxcns Bncr, C. W. (1950) Differential thermal anaiysis curves of carbonate minerals.Amer. M i.neral'. 35, 985-1013. Cerlr,ir.r, S. (1943) Contribution a l'6tude de I'hydromagn6siteet de quelquesautres hydrocarbonatesmagn6siens: l'hydrogiobertite, l'hydrodolomite et la giorgiosite. Bull. Soc.Fr. Mineral,.Cristal,logr.66, 55-70. FnNocr.ro,M. (1936)Ricerche sull'idromagnesite. Peri,od. Mineral.Tt 257-284. Ilsru-Cn.mlo, W. ano H. Hsmn-YnN (1965)On the mineralogicalproperties and origin of hydromagnesitefrom China. Sci,,Geol. Si,nica,ll, 37+-382. Jcisexc,O. (1960)Serpentine-magnesite deposits at Modum. NorgesGeotr. Und'ersdh.2l2, 5-8. - (1966) Geologiskeog petrografiskeundersdkelser i Modumfeltet. Norges Geol. Unil,ersbk. 235, 9l-97 . Lecnotx, A. (1905)Sur un nouveaumindral, la giorgiosite BuII. Soc.Fr. MineraL.Cri'stal'- Iogr.28,198-200. Lrncuurn, D. (1965)Stability of carbonatesin the systemMgO-COrHzO. J. Geol'.73, 730-754. L&snN, E. S. em H. Brnuax (1934)The microscopicdetermination of the nonopaque minerals (2nd edition). U. S. Geol,.Swr. BuIl. &8,30-32. MnNzeL, H. ANDA. Bnijcnran (1930) Studien an kohlensaurenMagnesiumsalzen. I. BasischeMagnesiumcarb onate. Z. Elektrochemie, 36, 63-87. Muurrox, F. A., H. W. J.lrru aNo C. S. TnoupsoN (1965)Coalingite, a new mineralfrom the New Idria ,Fresno and San Benito counties,California. Amer. Min- erd.50, 1893-1913. Munnocr, J. (1954)Unit cell of hydromagnesite.Amu. Minerol 39,24-29. NAstrln, B. (1965)Barringtonite-A new hydrousmagnesium carbonate from Barrington Tops,New SouthWales, Australia. Mi.nerol. Mog.34,370-372. War,rnn-Lfw, L. (1937) Carbonatesbasiques de magndsium.Ann. Chint'. (Pari's),7, l2r-224.

M anuscriptreceizteil, Ma.rch 3, 1970;accepted. Jor publ,icati.on,June 2, 1970.