American Mineralogist, Volume 69, pages 200J06, 1984
Santaclaraite,a new calcium-manganesesilicate hydrate from California
RrcHeno C. Eno U.S. Geological Survey, Menlo Park, California 94025
eNo Yosnrrezu Onasnr Department of Geology, University of Pennsylvania Philadelphia, Pennsylvania19104
Abstract
Santaclaraite,ideally CaMna[Si5O14(OH)](OH)' H2O, occursas pink and tan veins and massesin Franciscan chert in the Diablo Range, Santa Clara and Stanislaus Counties, Calif. It is associatedwith four unidentified Mn silicates, Mn-howieite, qtrartz, braunite, calcite, rhodochrosite, kutnohorite, barite, harmotome, chalcopyrite, and native cgpper. Santaclaraiteistriclinic,spacegroup Bl,a:15.633(l), b:7.603(l), c = 12.003(l)A,a= 109.71(lf,F = 88.61(1)',y:99.95(l)",Y = 13223Q)41,2= 4. The strongestlines of the X-raypowder pattern are (d,1, hkt):7.044, 100, 010; 3.003, 84, 501;3.152,80,410; 7 .69,63, 200; 3.847, 57, ( I 13,400); 3.524,39, 020. Crystalsare lamellarto prismatic (flattenedon {100}),with good cleavageon {100}and {010};H: 6%; D(calc.) : 3.398g/cm3, D(meas.) : -10.002), 3.31(t0.01);optically biaxial negative, with a : 1.681,F: 1.696,y = 1.708(all 2Vx:83 (tl)". Although chemicallya hydratedrhodonite, santaclaraitedehydrates to Mn-bustamite at about 550'C (in air). Santaclaraiteis a five-tetrahedral-repeatsingle-chain silicate and has structural affinities with rhodonite, nambulite, marsturite, babingtonite, and inesite.
Introduction about fifty abandonedmanganese mines located in Santa The new mineral santaclaraitewas discovered in 1975 Clara, Alameda, San Joaquin, and Stanislaus Counties in an abandonedmanganese mine in the Diablo Range in near their common junction. Nearly all these mines lie northeasternSanta Clara County, Calif., by Messrs.John within a circle of 16-kmradius centered on Mount Board- L. Parnau and Albert L. McGuinness, who brought it to man at this junction. The mines and the geology of the us for investigation. They suspectedthat the mineral was areawere describedby Jenkins(1943) and Trask (1950), inesite from its color and prismatic habit, but our studies and a review with later production figures was presented proved the mineral to be new and to have a crystal by Davis (1957).The manganeseore bodies in the four- structure that helps to clarify the role of hydrogen in county area are ofthe Coast Rangesedimentary type that pyroxenoids(Ohashi and Finger, 1981).The mineral is occur in chert of the Franciscan Complex (Jurassic to named for the County of Santa Clara, the locality of its Lower Tertiary). first occurrence. Specimens of santaclaraite (holotype Our present information from the discoverers is that and cotypes) will be depositedat the SmithsonianInstitu- the abandonedmine in which santaclaraitewas discov- tion (National Museum of Natural History), Washington, ered is on property that is now private, posted against D.C. The name and descriptionhave been approvedby trespassing,and patrolled by a securitysystem. The mine the Commission on New Minerals and Mineral Names, workings are no longer accessible,and all of the manga- I.M.A. A descriptiongiven by Ohashiand Erd (1978)of nese mineral specimenswere found on old dumps at this an unnamed new mineral was a preliminary report for site. santaclaraite. The paragenesisof the specimensthat we have seen from this locality is noteworthy in that the more common Occurrence and paragenesis Mn minerals are scarceor absent and the Mn silicates so far found are all unusual in some respects. It seems Although the discoverers of santaclaraitedid not dis- worthwhile, therefore, to give a detailed account of the close the exact location of its occurrence, they have associated Mn minerals. Santaclaraite occurs both as provided us with many specimensfrom the locality and cross-fiber veins (the largest measures I cm in width by partial information on the occurrence. The mine is one of more than 9 cm in length) and irregular masses(10 cm in 0003-004x/84/0I 02-0200$02.00 200 ERD AND OHASHI: SANTACLARAITE 201 maximum dimension) in Mn-oxide-stained chert and A secondoccurrence of santaclaraitewas discoveredat quartz. Though uncommon in its overall occurrence, the Buckeyemine (locatedin sections2 and3, T. 5 S., R. santaclaraite is the most abundant Mn silicate at this 5 E., in Stanislaus County, Calif.). The mineral was Iocality. The next most abundantMn silicate is an uniden- identified by Erd in specimens collected rn 1942-1944 tified reddish-brown fine-grainedmineral that appearsto from the ore body by Dr. Max D. Crittenden,Jr., during be a memberof the friedelite series.Three other unidenti- his study of the geology of the deposit (Trask, 1950,p. fied Mn silicatesat this locality are similar to, but differ in 287-289).Santaclaraite occurs sparselyas pink prismatic some respectsfrom, the minerals parsettensite,welinite, crystals up to 3 mm long in quartz veins in tan chert and gageite (all currently under study). Mn-howieite is associatedwith rhodochrosite, the friedelitelike mineral associated with santaclaraite as yellow-brown fibrous (identical with that of the Santa Clara Co. occurrence), veinlets,masses, and small spherules,with a : 1.697,B braunite, and very minor chalcopyrite. It is probable that : 1.716,y = 1.727(all 10.002).Fine-grained rhodochro- at least some of the "inesite" identified in the mine by site is subordinate to the Mn silicates but is widely Crittenden is actually santaclaraite(Crittenden, oral com- disseminated throughout them and the quartz matrix. munication, 1980). The underground workings at the Calcian kutnohorite and calcian rhodochrosite were abandonedBuckeye mine are no longer accessibleand an found in a single occurrenceas small scalenohedra(to 0.6 attempt to find santaclaraite in the present-day (1981) mm). The central cores of the crystals consist of massive dumps was unsuccessful. white Ca-kutnohorite(a : 4.919,c : 16.525A; a = 1.702, : -10.002) e 1.518,both encrustedwith tiny euhedral CrystallograPhY rhombsof Ca-rhodochrosite(a : 4.824,c = 16.0lA; c.r: 1.78510.003,a : 1.518t0.002).A strongpositive micro- Morphology chemical test was obtained for Mn, but Fe could not be Santaclaraite occurs principally as radiated lamellar detected.The data indicate about 20 mole percent CaCO3 aggregates(Fig. 1) composed of thin prismatic to tabular in the rhodochrosite, which is near the limit for naturally subhedral crystals, flattened on {100}. The rough spher- occuring material (Deer er al., 1962,p.265-267). All the ules averageabout a millimeter in diameter. Where space specimensthat we have seenare stainedblack with a thin permits, thick prismatic euhedra, up to a centimeter in coating of X-ray amorphous Mn oxide, although very length on [fi)l], are developed;several ofthese are visible little of this material is actually present. The Mn mineral in the vug in Figure l. The mineral also occurs in cross- that was mined at this locality appears to have been fiber veins composed of prismatic to nearly fibrous crys- braunite,which occurs as massesand veins, up to 6 cm tals having a length/width ratio up to 40. Forms identified acrossin the specimensthat we have seen.Other associ- with a two-circle optical goniometer are b {010}, a {100} ated minerals are calcite (some manganoan),barite, and the most prominentform, m {110},/{l0l}, g {301},and ft rare harmotome, chalcopyrite, and native copper. Some Simpletwinning on {100}is common' ofthe quartz is colored dark grayish blue by inclusions of {401}. asbestiformriebeckite. X-ray data The preliminary unit-cell dimensions of santaclaraite were determined from single-crystal X-ray precession photographsusing Zr-filtered Mo radiation. Table I lists these data, refined by least-squaresanalysis ofthe X-ray powder data. The crystal structure of santaclaraite has beendetermined by Ohashiand Finger(1981); the mineral has centric triclinic symmetry (Pl for the primitive cell). An /-centered cell was employed by Ohashi and Finger for structural comparison of santaclaraite with other pyroxenoids;however, a B-centeredcell is selectedhere on the basis of morphology for the mineralogic descrip- tion. Table I comparesthe data for the various settings. The X-ray powder data are shown in Table 2. There is a moderately strong preferred orientation of hlcOreflections in the X-ray diffractometer pattern due to the good {010} and {100} cleavages.The intensities observed in powder photographs agree closely with the calculated intensities preferred Fig. l. Vuggy radiated pink santaclaraite, with prismatic and so are not listed in Table 2. The effect ofthe : crystals of tan santaclaraite(larger is 7.5 mm long) projecting orientation is most noticeable for the lines at d 2.692 into vug at center. Photograph by Lowell Kohnitz, U.S. and 2.9394, which are the strongest in powder photo- Geological Survey. graphs. 202 ERD AND OHASHI: SANTACLARAITE
Table 1 Unit-cell data for santaclaraite Physical and optical properties Santaclaraiteis pale pink (Munsell color 5RP 8/2) or Sy6ten Tric 1inic Triclinic Triclinic moderate reddish orange (l0R 6/6). Although these two Sp€ce group !1 B1* r1* color varieties are quite distinctive, we observed no a (l) 9.738(2)** r5.633(r) 10.291(r) significant differences in their chemical composition or 9.970(r) 7.603(1) rr,934(2) 7.503(r ) 12,003(3) r2.oo3(4) optical properties. The color of the pale-pink variety 109.77(r)" r09.70(1)" 105.78(r). B 93.95(r). 88.6r(1)" 1r0.55(2)" darkensto orangewhen exposedto tungstenX-radiation. r04.97( 2 ). 99.95(1)' 89,09(r)" The mineral is transparent v (AJ) 651.0(r) r322,0(t 1322,0(4) and has a vitreous luster and a very pale pink streak. It is nonfluorescent. Cleavage is z 244 good on both {100}and {010}.Its hardnessis 6% (Mohs). D (s/c#) 3.398 (idealized compoaition) : 3.379 (chmical analysis) Santaclaraiteis biaxial negative:a 1.681,B: 1.696, : -t-0.002; = D 3.31(!0.01)r "y 1.708(all Na light); zvx 83(rl)"; r > v, moderate. The optical orientation is ZAc = 2", XAb = -21' in {Ifi)} sectionsi ZAc : 16",YAa : - 14.5"in {010} * Alterdetive settings used for Einer€logicel End sections. Thick sections of santaclaraite show a weak c46taI structursl descriDtions. CelI transfometion mairices are l- \ o\ t !o l: I orol frm rhe BT ro pl pleochroism, with X = very pale red, y : pale red, and Z ceII and [ 12lll2ll001] fron the BI to II ceII. : pale reddish brown; absorption is I > Z > X. The ** Data obteined frm refinenent of X-ray powder data (Teble 2), using the les6t-squsre6 progran of Applman optical properties were determined using a spindle stage and Evan6 (1973). Perenrhesized figuree represen! the estinated 6tanderd devietion (eed) in tems of least with X-ray oriented crystals. units cited for the value to their imediate left, thus 9.738(2) indicates en esd of 0.002. Chemistry
+ Det€mined in nethylene iodide/ecetone mixture checked sith a westDhal balance. Analyseswere made of both pink and tan santaclaraite, using the Geophysical Laboratory MAC electron micro-
Table 2. X-ray powder diffraction data for santaclaraite
* CaIcu leted Obaerved** Calculated Obeerved** hkt Erkr(A) -!I dhk r( A) hkl dhk g( A) _! dhkr( A)
200 7,694 44 63 7,69 313 2.666 L9 4 2.666 010 7.048 85 100 7.04 52L 2.6LO 26 20 2.609 1r1 6.L42 lt 4 5. 15 610 2,558 2.557 210 JJ JO 4,797 131 2.5L2 18 II 2.51I 311 4.5L4 64 4.518 331 z.tssl 8 2.399 420 2.398) 31I 6 3.969 113 r . aas] 521 2,380) 24 57 3.847 2 2.378 400 3.847) 115 2.378) t2l 3.791 2 3.791 2,353 2L 2.353 4I0 J.O)O 3,652 1 2.743 7 2,238 212 3.598 o 3.598 020 3.524 16 39 3.524 2.209 222 3.458 11 5 J.4)b 38 2,200 220 3.438 4 3.44L 4 2.15L 32L 3,312 5 1 11' II 2.r44 4 2.118 4L2 3.287 I1 5 3.290 410 )) 80 3.L52 2,058 402 I3 8 3.125 5 2.052 511 r.oor) 2 2.O23 501 2.997| 88 84 3,003 2 I .920 014 2.9e3) I.872
113 2.937 89 l3 2.939 o 1.E65 L2l 2.930 58 t3 2.932 4 l.836 32r 2.454 8 6 2.853 6 L. t6l 32L 2.801 6 4 2,801 6 L.707 o24 2,691 100 7 2.692 20 r.682
PIus additional linee all with I ! 15
* All linee are indexed to Alkr 5 2.3501. Indicee fron lea€t-aquares analyeis of x-ray poeder data, using the digital-conputpr PrograE of Applefrenand Evans (1973). Intensities calculated by € progrsn of snith and Holmany (1978). ** x-ray diffrsctmeter conditions are: chart No. x3917; cu/Ni radietor; rCuKcl=l.540598A; eilicon used as internal standard; acanned at l/4" per ninute flom 4-100. 2e, ERD AND OHASHI: SANTACLARAITE 203 probe with an accelerating voltage of 15 kV and a Table 4. Chain silicate minerals with five tetrahedral repeats specimencurrent of 0.05 g.A. The results of the analysis are shown in Table 3. As noted Mlncill nroa Idralizsd chcolcal fomulr Raflrenca to of the tan santaclaraite eryltal ltructutc above, the analysisof the pink material is so similar that it is not reported here. The matrix corrections made are srntlcleraitc c!Mn4lsi50t4(oH)l(oil)'H2o tll (1968) pro- those proposed by Bence and Albee and Rhodonlte GaMn4[8i50151 I2l grammedby Finger and Hadidiacos (1972)for the micro- Babingronite ca2(Fe2+,Mn)Fe3+tsi5or4(oll)l t3l probe-analysissystem. The standardsused (Table 3) were (Li,Na)un4[si5o14(oH)l t41 selected on the basis of the beta factor in the Bence- Ndbulite Albee method.There is "superior" agreement(l-Kp/K" l,rarsturite Nacaun3[si5ot4(oH)] I5l = +0.002) between the chemical data, optical data, and rnesite ce2nn7[si16026(oH)2]'5H20 t51 specificgravity, using the compatibility index of Mandar' (I98I). ino (1981)for the Gladstone-Dalerelationship. lll oheshi eod Finter (1975). The formula of santaclaraite, obtained by combining l2l gl:, Peacor end Niizeki (1953), ohashi aod Finger the electron-microprobe analysis data of Table 3 with [3] Araki and zoltai (1972). (1981), (1977). the crystal-structuredata of Ohashi and Finger [4] Narita et el. (1975), Murakemi et al. is: (Cao.ezNao (Mn3.LMgoosFe6.trNi0 0rCoo or) [(Sis o+ or) [ 5 I Peicor et aI. ( 1978) . Alo.otOr+.og(OH)0.e71(OH)'HzO,or, ideally' CaMna [5] t{en and Ghoee (1978). [Si5Or4(OH)](OH)' H2O. All manganesewas assumedas Mn2+ in calculating the above formula. This assumption is based on Mn-O bond distances (around 2.2L) for santaclaraite(Ohashi and Finger, 1981). 4): these minerals all have silicate chains with five tetra- Santaclaraiteis insoluble or only very slightly soluble hedral repeats and bands of octahedral cations' Inesite, in hot concentratedacids. When the mineral is heatedin a which is visually very similar to santaclaraite,is a double- closedtube, a moderateamount of water is driven off (pH chain silicate (Wan and Ghose, 1978): the others are = 5), and the mineral turns light brown; with stronger single-chainsilicates. heating, to about 1000"C, the mineral turns white iind The numberof hydrogenatoms (e.g., per five silicons) nearly opaque. of santaclaraite is higher than those of babingtonite' nambulite. and marsturite but less than that of inesite' If Related minerals only chemical formulas are considered' incorporation of Santaclaraite is chemically a hydrated rhodonite, al- hydrogen into an anhydrous formula M2+5Si5O15or though structurally hydrogen atoms play three different M2*1sSi1sO3scan be accomplished by the following roles (for structural discussion see Ohashi and Finger, changes: 1981).In addition to rhodonite, several minerals are known that are structurally related to santaclaraite(Table Table 5. Unit-celldata for Ca-bustamite,Mn-bustamite, and dehYdratedsantaclaraite Table 3. Electron-microprobeanalysis of santaclaraite Ca-bust@i te lln-bustdite Dehydrated xP-I l8* uP-Iol* santaclaraile* cetion. (be.ed crlc. c6pn. (utZ) for oD 17 oxyten.) cro .rrHno.58i02.2H20 GaSiO3 (tlZ) 33.E 24(? )
SiO2 44,74* s i4* 5.045 44.42 spec€ ttdp Al AI AI Al 203 0, 12 A13+ q.qr!.- F:..q6r USo 0.3I ''rl-i 0,052 a (l) 7.848(3) 7.639(3) 1.616(2) MnO 4L.26 l{nz- 3.941 41.96 b 7.263(5, 7.098(4) 7.090(3) F.0 0.09 Fc2+ 0.008 c 13.968(1) 13.726(2, r3.5r5(3) Nio 0,06** Ni2* 0,005 i go.re(r). 89.72(3)" 89.94(3 )' Coo 0.05*r Co^2: 0.005 F4'0lI g 95.25(2r' 94.82(2)" 94.44(2)' Cao 7.24 c.'- 6'.E-75----- 8,29 , 103.36(3)" 103.07(3 )' r03.37(3)' Ne20 0, 12 Nalt 0.026 r-0.90I ri for un; Yolhikazu oheshi' !!gIIgL. Standards ured: ttiPhylite foroterice for Fc; a tles. of dioPside65-jadeite35 cmpo.itioa speci*os fro Eroken ni11, x.S.lJ., AustEalie' de6cribed by for Na, M8, end A1; rcl1eltonite for Si and ce; orthoclese for K. lk3on (1973). Data obtained fr@ refinfieDt of x-ray Posde! d.ta (Teble 5) ueing the leaat-5q@res progre of APPlman Detetuined by Jun Ito (written cm., 1977), usint both etdic lod Bvan6 (1973). Brror in psreDthedes is one stendsrd abrorption snd sp.ctroscoPic rethoda. Also Preaent erei deviltioD. V2O5<0.01 utl; Ba' St, Ti, end Cr <0.001 *tl. SrntaclaEait€ he.ted itr eir st approxiMtety 1'000'C for uicr@oulmetric de!€minetion by uarcelyn crmer (U.s' five h@i.. eeological Survey). Average of teo detedinetione on 46- and 3418 senple6. Data frd l{econ (1973). 2M ERD AND OHASHI: SANTACLARAITE Table 6. X-ray powder diffraction data for Ca-bustamite,Mn-bustamite. and dehvdrated santaclaraite Ca-bustamite lln-bu6tenite Dehydr.ted l{P-10 1 + r Santacleraite++i hkt (t) --E.Eld- - I d-. (a) I r d.. (A) I g!E/A) il qk,( r) - -!!& hkr 200 7 .602 l0 7.62 3I 21 7.4I 10 7.4L4 100 002 6.954 6.95 5 6.84 17 6.79 7 6.E35 002 202 5,388 5.39 4 5.267 rO2 202 4.908 l3 4.905 2 4.827 16 4.815 18 4.E15 102 4.5r8 t3 <1 4.404 5 --- 4.4L9 llr 400 3.801 23 3.803 3.707 86 3.696 25 3.707 200 311 3,676 I8 2 3.591 E 3.58r 3,571 211 004 ';J 3.421 96 3.394 3.474 50 3,418 004 402 3.474 3.390 24 3.389 202 3.409 1.344 l0 3.337 r13 204 3.280 3.279 100 3.219 100 3. 182 41 3.2t5 r04 402 3.211 4 3.2tr 6 3.144 r0 3.t44 6 3.t42 202 222 3.t74 3.O92 3.104 022 204 3.056 49 3.055 35 3,005 70 2.997 56 3.003 104 511 3.046 4 2.967 8 2.977 2lr 420 2.957 s6) 2.893 11 2.882 2.95L II 100 2.492 r20 220 2.95r roo) 2.871 t0 2.474 220 222 3 2.695 2.704 222 404 2.594 13 2.695 24 2.635 33 2.604 t2 2.633 204 2.605 5 2.606 2 2.566 7 2.538 2.556 015 2.573 8 2.574 2 2.5t9 7 2.525 r15 600 2.534 2.535 l) 2.470 70 2.463 l5 2.471 300 224 2.455 (z.t*tz o24 '3J 2,454 2.407 16 2.400 2l 404 2.454 lz.+ot 2o4 620 2.332 l2 2.273 I5 2.283 220 ---'t T (z.zet n5 006 2.3t8 2.319 9 2.27E t2 rl lz.zla 006 602 2.3t2 1 2.313 12 2.26I E 2.260 302 206 2.277 31 '::'" 2.213 2.215 106 2.r90 4 -:2 !:1'u -:i 2.t45 7 2.141 224 522 2.t25 5 2. 116 29 222 422 2.163 20 2.163 4 2.109 7 2. IOE 322 604 2. r45 5 2.t45 6 2.093 1l 2.071 6 2.O94 304 406 2,067 3 2.024 l0 2.000 4 2.O24 206 424 2.005 5 ?:-o-uu -1: 1.941 5 r.955 324 604 1.962 8 t-:-"-" r.921 IO t.922 304 226 r.92t --: \:" _19 1.875 7 1.8E9 L26 E00 1.900 3 1.900 t2 I.853 l0 1.846 1.853 400 820 1.864 s) 1.E13 I.864 r L.E26 6 t2 t,824 320 620 L.864 4l 1.814 6 I .813 420 622 r.838 1.E37 I r.7 a9 422 240 1.816 1.776 l6 t.774 r40 802 1.791 3 1.750 1r 1.745 1.750 402 426 1.779 4 r.749 126 l_1" _: 1,740 226 3 1.738 226 008 I.73E I9 1.739 18 1.708 44 t.697 I6 r.709 00E Plue eddirioMl lioe6 elt wirh I 5 13 Indices for ttre fi unit c€ll and d (ca1c.) frm the lees!-squeres enslysis of the Ca-bucteite x-rey Powder dsta using the diSital cmputer progrsn of Applfren and Evans (1973). Calculsted intensities fron Borg end soith (1969); dete based on the 6trucrure deteminsrion of busrmite (54.5 noleZ caSior) frm- Frsnklin, N.J., bI Peecor and Buerger (1962). Indicee for the A1 unit cell sDd d (catc.) fro the least-squ€res eMlysis of the ltn-bust@ite x-rsy poeder data. + Cs-bust6ite (78,8 ooleZ CeSiO3) fr6 Broken Hi11, l| S.t{., Austrelia (}{ssoD, 1973). X-ray diffrect@eter conditione ere: Chert No. X39OO; Cu/Ni rediation; )CuKal=I.5405981; Si used es intemal stsndard; scenned at l/4' per minute froE ll-92" 2e. it un-bu3teoite (33.8 noleZ Cesio3) frm Broken ltiltr N.S.tf., Ausrralie (ila3on, 1973). X-ray diffrectdeter conditioDg ar€: ee ebove, ercept Chert No. X3E94; scanned frm 6-102. 2e. i+t sentaclareite heated in sir et epproxinetely 1,000"C for five hours, X-rey diffract@eEer condition6 are: as ebove, except Chlrt Io. X3902; €csnned froD ll-106. 2g. H ' ' O, are responsible in the case of santaclaraite (Ohashiand Finger, l98t). The geneticrelationships such as hydration and dehydration, however, are not known at present among the minerals listed in Table 4. When o il, santaclaraiteis heated, it does not transform to either o CaMna[SisOra(OH)]or CaMna[SisOrs],but the tetrahe- o o dral repeat length changes,as is discussedin the next o section. Thus this relation for santaclaraite is another o pyroxenoids o example of a phase change between or o pyroxenes with ditrerent tetradedral chain repeats (Mori- moto et al., 1966,for johannsenite-bustamite;Glasser and Glasser, 1961,for rhodonite-wollastonite;Aikawa, 1979,for rhodonite-pyroxmangite). Dehydration to Mn-bustamite We found early in our study that santaclaraitedehy- Vm (cm3) drates in air at a low red heat to form Mn-bustamite. This Fig. 2. Molarvolume (Vm) vs. mole percentage of CaSiO3for reaction has been described at length by Ohashi and bustamiteand dehydrated santaclaraite. Ferrobustamite: Fe-BSt Finger (1981)and, although the mechanismis not dis- (Tsusue& Matsuoka,1979), FeBSo (Yamanaka er al' ' 197'l).Ca' cussed further here, it is of interest to compare the bustamite:MP-138 (Mason, 1973, molar volume determined in dehydration product with naturally occurring bustamite. this study), Ca-BS(Ohashi & Finger, 1978).Bustamite: PB (Ohashi l97E)'H Unit-cell (Table 5) and X-ray powder diffraction (Table 6) (Peacor& Buerger,1962), BS & Finger' (Harada 1974,volume recalculated). Mn-bustamite: MP' data are listed for dehydrated santaclaraiteand for two et at., l0l (Mason,1973, molar volume determined in this study)'Mn- bustamitesfrom Broken Hill, N.S.W., Australia, that BS(Ohashi & Finger,1974),Y'f (Yamanaka & Tak€uchi,l98l). contain78.8 and 33.Emole percentCaSiO3 and represent Dehydratedsantaclaraite: DSC (this study). nearlylimiting compositionsof bustamite(Mason, 1975). Agreement between the powder diffraction data of dehydrated santaclaraite and these two bustamites is amount of another phase or phases; these minor phases excellent except for the intensity data. The X-ray diffrac- are either X-ray amorphous or insufficiently abundant to tometer traces of Ca- and Mn-bustamite (Table 6) show a contribute to the X-ray ditrraction pattern. In any case, strong preferred orientation due to good cleavages on the Mn-bustamite produced by heating santaclaraite {100} and {001}. The strongestreflection in the calculated above 550'C (Ohashi and Finger, l98l) must contain pattern (Borg and Smith, 1969) and in X-ray powder substantially less CaSiO3than the limiting mole ratio of photographs prepared from a spherical mount is for d l/3 found for naturally occurring bustamite (Mason, 1975; (220). The strongest line,_without exception, for diffrac- Ohashiand Finger, 1978).Abrecht andPeters (1980), who tometer traces is for d (204').This orientation effect is have synthesizedMn-bustamite containing about 20 mole minimized in the pattern of the Mn-bustamite produced percent CaSiOr, suggestedthat this result may indicate by heating santaclaraite as the transformation is not disorder in their synthetic high-temperature Mn-busta- topotactic (Ohashiand Finger, l98l), and the observed mite. However, a recent study by Yamanakaand Takdu- intensities agree much better with those calculated from chi (1981)has shown that a natural rhodonitewith 18.10 the crystal structure. mole percent CaSiO3 could be transformed into busta- When the mole percentage of CaSiO3 in naturally mite. The plot of mole percent CaSiO3 versus molar occurring bustamites is plotted against their molar vol- volume for their inverted bustamiteplots very near to that umes, the curve is seento be essentiallylinear (Fig. 2). of dehydrated santaclaraitein Figure 2. The slope of this line differs slightly from, but agrees reasonably well with, that given by Abrecht and Peters Acknowledgments (1980,p. 265, Fig. 6). Extrapolationof this line suggests that the Mn-bustamite produced by dehydration of santa- Wethank Messrs. John L. Parnauand Albert L. McGuinness us with a claraite should contain about 24 mole percent CaSiO3for for the santaclaraitespecimens and for furnishing partial of the discoverysite. Permissionto visit the the molar volume observed.On the other hand, if the bulk description Buckeyemine was granted us by Messrs.Rolland Seegers and composition of dehydrated santaclaraite(17.7 mole per- ManuelGonzales; specimens from the minewere provided by cent CaSiO3)represents only Mn-bustamite, then the thelate Dr. Max D. Crittenden,Jr. We areindebted to Dr. Brian molar volume should be approximately 35.4cm3 or have a H. Mason,of the SmithsonianInstitution, Washington, D. C., cell volume of about 70543. That such is not the case for specimensof Ca- and Mn-bustamitefrom Broken Hill, suggeststhat when santaclaraiteis dehydrated by heat- N.S.W.,Australia. This studywas partly supported by National ing, it transforms chiefly to Mn-bustamite plus a minor ScienceFoundation Grant EAR-77-15703. The manuscript bene- 206 ERD AND OHASHI: SANTACLARAITE fited from reviews by Drs. Judith A. Konnert, EugeneE. Foord, Lithium-hydrorhodonite. Acta Crystallographica, B33, 919- Peter Robinson, Howard W. Jaffe, and Donald R. peacor. 921. Narita, H., Koto, K., and Morimoto, N. (1975)The crystal References structure of nambulite (Li,Na)MnrSisor4(OH). Acta Crystallo- Abrecht, J. and Peters, Tj. (1980)The miscibility gap between graphica, 93 l, 2422-2426. rhodonite and bustamite along the join MnSiOr_Cao.eo Ohashi,Y. and Erd, R. C. (1978)A new pyroxenoid MnaCa- ' Mn6a6SiO3.Contributions to Mineralogy and petrology, 74, Si5Or5 2H2O: its structural relationship to rhodonite, nambu- 261169. lite and marsturite (abstr.). Geological Society of America Aikawa, N. (1979)Oriented intergrowth of rhodonite and pyrox_ Abstracts with Programs, 10, 465. mangite and their transformation mechanism. Mineralogical Ohashi,Y. and Finger,L. W. (1975)Pyroxenoids: a comparison Journal (Japan),9, 255-269. of refined structures of natural rhodonite and pyroxmangite. Appleman,D. E. and Evans,H. T., Jr. (1973)Job92l4: Indexing CarnegieInstitution of Washington Year Book 74, 564-569. and least squaresrefinement of powder diffraction data. U.S. Ohashi, Y. and Finger L. W. (1978)The role of octahedral Department of Commerce, National Technical Information cations in pyroxenoid crystal chemistry. I. Bustamite, wollas- ServiceDocument PB-216188. tonite, and the pectolite-schizolite, seranditeseries. American Araki, T. andZoltai,T. (1972)Crystal structure ofbabingtonite. Mineralogist, 6f , 274-288. Zeitschrift ftir Kristallographie, I 35, ?55-37 1. Ohashi,Y. and Finger, L. W. (1981)The crystal structureof Bence, A. E. and Albee, A. L. (1968)Empirical correction santaclaraite,CaMno[Si5O,a(OH)](OH) . H2O: the role of hy- factors for the electron microanalysisof silicates and oxides. drogen atoms in the pyroxenoid structure. American Mineral- Journalof Geology,76,382-403. ogist,66,154-168. Borg, I. Y. and Smirh, D. K. (1969)Calculated X-ray powder Peacor, D. R. and Buerger, M. J. (1962) Determination and patterns for silicate minerals. Geological Society of America refinement of the crystal structure of bustamite, CaMnSi2Ou. Memoir 122. Zeitschrift fiir Kristallographie, I I 7, 33l-343. Davis, F. F. (1957)Manganese. In O. p. Jenkins and L. A. Peacor, D. R. and Niizeki, N. (1963)The redetermination and Wright, Eds., Mineral Commodities of Califomia: California refinementof the crystalstructure of rhodonite,(Mn,Ca)SiO:. Division of Mines and Geology Bulletin 176,325-339. Zeitschrift fiir Kristallographie, l 19, 98-l 16. Deer, W. A., Howie, R. A., and Zussman,J. (1962)Rock_ Peacor,D. R., Dunn, P., and Sturman,B. D. (1978)Marsturite, FormingMinerals, Vol. 5, Non-silicates.Wiley, New york. MnrCaNaHSirOl5, a new mineral of the nambulite group from Finger,L. W. and Hadidiacos,C. G.(1972)Electron-microprobe Franklin, New Jersey.American Mineralogist, 63, I187-1189. automation.Camegie Institution of Washingtonyear Book 71, Smith, D. K. and Holomany,M. (1978)A FoRTRANtv program 59E-600. for calculating X-ray powder ditrraction patterns-Version 7. Glasser,L. S. D. and Glasser,F. p. (1961)Silicate transforma- The PennsylvaniaState University, University Park, Pennsyl- tions: Rhodonite-wollastonite. Acta Crystallographica, 14, vania, p. l-63. 818-822. Trask, P. D. Ed. (1950)Geologic description of the manganese Harada, K., Sekino, H., Nagashima,K., Watanabe.T., and depositsof California. California Division of Mines and Geolo- Momoi, H. (1974)High-iron bustamite and fluorapatite from gy Bulletin 152. the Broken Hill mine, New South Wales, Australia. Mineral_ Tsusue,A. and Matsuoka,M. (1979)Ferrobustamite from the ogical Magazine, 39, 601-604. Tsumo mine, ShimanePrefecture, Japan. Kumamoto Journal Jenkins, O. P. Ed. (1943) Manganesein California. California of Science,Geology, ll, l-9. Division of Mines and Geology Bulletin 125. Wan, C. and Ghose, S. (1978)Inesite, a hydrated calcium Mandarino, J. A. (1981)The Gladstone-Dale relationship: part manganesesilicate with five-tetrahedral-repeatdouble chains. IV. The compatibility concept and its appliation. Canadian American Mineralogist, 63, 563-57l. Mineralogist, 19, 441450. Yamanaka, T. and Tak€uchi, Y. (1981) X-ray study of the Mason, Brian (1973)Manganese silicate minerals from Broken rhodonite-bustamitetransformation. Zeitschrift fiir Kristallo- Hill, New South Wales. Journal of the Geological Society of graphie,157, l3l-145. Australia, 20, Pt. 4, 397-404. Yamanaka,T., Sadanaga,R., andTak6uchi,Y . (1977)Structural Mason, Brian (1975) Compositional limits of wollastonite and variation in the ferrobustamite solid solution. American Min- bustamite. American Mineralogist, 60, 2Og-212. eralogist,62, 1216-1224. Morimoto, N., Koro, K., and Shinohara,T. (1966)Oriented transformation of johannsenite to bustamite. Mineraloeical Journal(Japan), 5, 44-64. Manuscript received, June 30, 1982; Murakami, T., Tak€uchi, Y., Tagai, T., and Koto. K. 0977) accepted for publication, May 25, 1983.