Canadian Minelalogist Yol.26, pp. 9ll-916 (1988)

CHESTERMANITE,A NEW MEMBER OF THELUDWIGITE_PINAKIOLITE GROUP FROMFRESNO COUNTY. CALIFORNIA

RICHARD C. ERD U.S. GeologicalSumey, tuis sto, 345Middlefietd Road, Menlo Park, Colifornia94025, U.S,A. EUGENE E. FOORD U.S. GeologicalSurvey, MS 905,Box 25046,Federal Center, Denver, Colorado 80225, U,S,A

ABSTRAcT taux prismatiquesatteignent 2 rnm sur [@l] et sontapla- tis sur {010};les formes importantas sont {ll0}, {210}, Chestermanite,ideally Mg2@d.+,[14g,Al,Sb5+)BO3O2, et {010}. La chestermaniteest vert grisetre d noir (dansles is orthorhombic, spacegroupPrnm o7Pnn2, a 18.535(3), cristauxplus grossiers), et possddeun €clatvitreux i soyeux; b n.n3\), c 6.93(l) A, v tZll.l1Z\ it3, Z = 16.Chesrer- H = 6, D^o3.12Q), D."6 3.650; in€gale i con- manite occurs in association with magaesiancalcite, lud- choidale;non-fluorescente et non-magndtique. Elle est biaxe wigite, , wightmanite, two undescribed borate positive,no 1.753-1.759,np 1.763-1,767,n" 1.791-1,797 , spinel, brucite, safflorite, and ldllingite in a small (t0.002), 2V263"(calc.). Les huit raiesles plus intenses brucite marble body in the Twin Lakes region, northern du clichd de poudre obteuu par diffraction X ld en Fresno County, California, U.S.A. Microprobe analysis L(r\(hkt)l sont: 5.114(100X220),2.559(91)(440), gaveAl2O3 5.3, Fe2O316.0, Sb2Oj 10.3,TiO2 0.8, MgO 2.r69(s7)(820), 2.746(34)(530), | .9975(32)(260), 48.0, MnO 0.1, CaO 0.1, B2O3(calc. for B = 1) 18.22,F 2.415(19)(412), l.53m09xle22), 1.707 l(17)(6@). Le nom 0.1, less,OeF 0.04,sun!,98.88 wt. 70, correspondingto honoreM. CharlesW. Chesterman,geologue de la divi- gdologie (a Mc2Gd jsM&.2sAb.r9sbd.i2Tr0.0r1.ooBOr(Or.seF o.or)rz.oo. sion desmines et de de l'6tat de la Californie Typically fibrous; rare prismatic crystals extend to 2 mm la retraite)qui I'a d€couverte. on [@l] and are flattened on predominantforms {010}; par are {ll0}, {210}, and {010}. Chestermaniteis greyishgreen Cfraduit la Rfiaction) (to black in coarsecrystals) with a vitreous to silky luster; H = 6, Dm 3.72Q), Dcak 3.650 g/cm3; uneven10 con- Mots-cl6s:chestermanite, nouvelle espdce mindrale' borate choidal fracture; nonfluorescent, and nonmagnetic. demagndsium, fer, aluminiumet antimoine,groupe de Chestermaniteis biaxial positive, no 1.753-1,759, n6 la pinakiolite,Californie. 1.763-1.767,nrl.79l-1,797 (aU 10.002),2V"63' (ealc.). The strotrgeslreflections in the X-ray powder-diffraction - patterntd in A(4 @k[)l are5.1 l4(100X220),2.559(9r)(W), INTRoDUCTToN 2.169(57)(820), 2.7 46(34)(s30), | .9975(32)(260), 2.4'75 (r9r(4r2), 1.53@(19X10.22),1.707 I (17)(660).The The new speciesdescribed herein was dis: new speciesis named to honor its discoverer, Mr. Charles covered by Mr. Charles W. Chestermanin 1980in W. Chesterman, retired geologist of the California Divi- the course of his long-term (1938 to present) study sion of Mines and Geology. of the geology of the Twin Lakes regon, northern Fresno Coun8, California. He furnished us with the Keywords: chestermanite,new mineral species,magnesium preliminary aluminum antimony borate, pinakiglils goup, orieinal malerial and, after investigation, California. we reco$ized it to be a new species.We havenamed the mineral in honor of Mr. Chesterman,retired ge- SoMMerns ologist of the California Division of Mines and Ge- ology, who has had a distinguishedcareer over many La chestermanile, de formule id€ale years as both a geologist and a mineralogist. The Mg2@e3+,Mg,Al,Sb5+)BO3O2rest un€ espacenouvelle mineral name and description have been approved orthorhombique, groupe spatial Qtnn ott Pnn2,o o by the eommission on New Minerals and Mineral 18.535(3),b D.n30), c 6.043(l) A, V r374.7Q) A3, Names, I.M.A. After completion of studiesof as- Z = 16, EUe est associ€ed magndsienne,, sociatedminerals, the holotype specimen(80-PP-2) fluoborite, wigbtmanite, deux autres espicesborat6es nou- and cotypic material will be preserved at the U.S. velles, spinelle, brucite, safflorite, et lOllingrte, dans une National Museum, Washington, D.C. (NMNH petite enclavede marbre brucitique dans la rdgion de Twin Lakes, du secteurnord du comte de Fresno, en Californie 165968). (E.-U.). Les analysesi la donnent:AI2O3 5.3, OccURRENcE Fe2O316.0, Sb2O5 10.3, 1 MgO 48.0,MnO 0.1, CaO 0.1, B2O3(obtenu en B = l) 18.22,F 0.1, moins O=F 0.04, total 98.8890,en ce qru cores- Chestermanite occurs in a contact-poly' pond i Mg2(Fefl| li2Tio.otEr.ooBo3metamorphosed septum that lies between the Mt. (Or.seFo.or)82.m.Elle est De rares cris- Givens and Kaiser Peak plutons of tle central Sier- 911 912 THE CANADIAN MINERALOGIST ra Nevada. Details of the geology were given by manite has numerous, uniformly distributed and Chesterman(1942, 1959),Hamilton (1950, Bateman sized (about 2 pm diameter), equant, anhedral inclu- et al. (7971), and Kerrich et al. (1973). The exact lo- sions of an unidentified mineral, but most chester- cation of the type (and, so far, only) occurrence is manite is relatively free of included matter. No signs 37"17'35'N,and 119o08'0.25'W, intheSW /aNE of its alteration could be detected. y4, sec.28, T.7S., R26E., MDBM, of the Kaiser Peak 7%-minute topographic quadraneleof the U.S. MORPHOLOCY Geological Survey. The new mineral occurs in a small lens of brucite ChestermaniteOpicatly is fibrous (Fig. l) to asbes- marble, approximately 370 m2 in area, encasedin a tiform; the crystals atlatn 1.6 mm in length by 2 pm - skarn that is surrounded by in diameter (€neth/width = 800), and are commonly schistsand hornfels. The metamorphosedsediments curved along {001}. There is a continuous gradation are transected by dykes and sills of granodiorite. in size from the asbestiform crystals, through aci- Chestermaniteis found as veinlets 2 to 20 mm thick cular, to coarse prismatic crystals as much as 2 x and as sparsedisseminations in the marble along at 0.33 x 0.06 mm in size (eneth/width = O. The least 34 m of the marble's southwesterncontast with coarsecrystals are scarceand difficult to distingpish the magnetite-forsterite skarn. The most abundant from the associatedmagnesian-aluminian ludwigite. chestermanitewas found at the point of original dis- Crystalsare elongate[001] and flattened on {010}. covery at the baseof a thick layer of marble in a Gcm In cross-sectionthey are approximately diamond- thick band, colored light green by the mineral, 0.6 shaped, similar to, but more flattened than' the m from the marble-skarn contact. The chestermanite accompanyingludwigite, and are commonly slightly fibers are concentrated along, and distorted to fol- curved. Predominant forms, identified with a two- low, the boundaries of the recrystallized grains of circle optical goniometer, are (in order of decreas- calcite. The fibers are intimately associatedwith an ing importance){110}, {210}, and {010}. Forms earlier-formed magdBsian-aluminian ludwigite and {100}, {130}, {r20\, {2301,{540}, and {320} have a zincian-ferrian dodecahedral spinel that will be also been identified; no terminating forms were described in a separate report. Other associated found. All crystalsare finely striated parallel to [0] l]. minerals are fluoborite, wighfuanile, two apparently new borate minerals (under study), brucite, an iron X-RAY CnvsrellocnepsY analog of safflorite, lOllingite, and magnesiancalcite. Chestermanitefibers have beenobserved transect- Eight crystals of chestermanitewere selectedfor ing the earlier ludwigite, but most fibers flow around precessionstudies; zero- and fustJevel photographs or envelop both ludwigite and lOllingite. The lud- for the a, b, and c axes, and cone-axisphotographs wigite is somewhat ragged and appears to show for c, were obtained using Zr-filtered MoKa radia- effects of solution in some instances, but no signs tion. Chestermaniteis orthorhombic, spacegloup of alteration are visible. Chestermanite commonly Pnnm $trobable) or Pnn2 (possible),with unit-cgll is found as inclusions in the associated spinel, parametersq 18.535(3),b 12.273(l)'c 6.043(l)A, oriented parallel to [011] of the spinel. Somechester- V 1374.7Q)43, Z:16. Chestermanitethus appears to be isostrustural with orthopinakiolite (Takduchi et al. 1978), However, relatively long (60 hr.) exposuresare required to observethe true symmetry; i*/ reflections with / odd are very weak and diffuse, indicating structural defects that are characteristic of somemembers of the pinakiolite group (fak6uchi et al.1978,Bovin and co'ivorkers 1980' 1981, 1981a, l98lb). In contrast, the subcellwith c/2 of the lud- wigite structure type (Pbam or Pba2) shows strong and sharp reflegtions. High-resolution transmission electron microscope (HRTEM) images of chester- manite (taken by Dr. Jan-Olov Bovin) show clearly tJreorthopinakiolite strucfurewith a c repeat of.6.M4 A in the electron-diffraction pattern recorded along [010]. The HRTEM studies(electron-diffraction and crystal-structure images) by Bovin were performed on the finely fibrous crystals of chestermanitethat were found in the early stagesof our study, and no corresponding investigation has been made to date Frc. l. SEM photograph of fibrous chestermanite. of the thicker acicular crystals that are now avail- CI{ESTERMANITE, A MEMBER OF TIIE LUDWIGITE-PINAKIOLITE GROUP 913 able. There is evidence(Cooper & Tilley 1985)that EegIa 1. PoIIDER DAIA FoR CESTERI,IANIXI materials having the ludwigite structure can be 3 directly transformed to the orthopinakiolite struc- hkt {(exc)l qtoo"t2 1(rel) ture under the influence of the electron beam. 110 10.233 t 0.23 However, Cooper & Tilley stated that the ludwigite 200 9.267 fragments are stable under normal imaging condi 2LO 7.X 7.375 020 6.133 L2 tions. Confirmation of the original orthopinakiolite L20 5.A26 5.424 structure is provided by our long-exposure 3LO 5.519 4 X-ray- 220 lo0 (100) precessionphotographs. 400 4.634 l:l'o

The X-ray powder-diffraction data (Table l) 320 4.354 obtained with an X-ray diffractometer show strong 410 4.335 130 3.995 3.994 preferred orienlation for &&0reflections. The strong- 3.743 3.7X7 est intensities for a Debye-Scherrer photograph of 420 3.694 3.549 3.54a a randomly oriented (spheremount) specimen(Iable 330 3.4t1 3.411 040 3. O6a 1) contrast greatly witl those seenin the diffrastom- 3.067 15 430 3.067 eter pattern. There are no reflections visible in either pattern, N2 3.O22 however,for hklwilh I odd, evenwith long 6to 2.996 2.994 exposures(Z) hours, using a fine-focus X-ray tube). 240 2.9L3 2-goa 2.74 340 2.746 34 530 2.747 PHYSIcALAND OPTTcALPnopsnrrss 440 2.559 402 2.531 2.529 5 (80) 4L2 2.479 2.475 Ihe typical fibrous crystals of chestermanite 150 2.433 (ppproximately 2.433 13 0.03 mm or less in diameter) are 270 2.41L greyishgreen (Munsell Color No. l0 G 4/2), whereas s40 2.364 2.365 ao0 2.3L6 the less common thicker crystals are black. The 350 2.25L 2.242 is a paler ereyish green (5 G 5/2), and the 332 2.262 2.2U 450 2.L69 2.L69 luster is vitreous to silky. There is notable iridescence 820 2. l6a on the thicker black crystals, owing apparently to 2.M7 2..U6 the finely striated surface acting as a diffraction 060 2.U6 The surfaces of larger crystals of chester- 2.038 2.036 8 (70) erating. 260 L.9974 1.9975 manite, in fact, closely resemblethe magnified sur- 442 L.9524 3 face of a phonograph record in color, luster, and uo L.9524 360 1.94r.S L.94L5 9 iridescence. 632 1.9102 t.9100 graity 460 1.S713 1.8704 5 The specific of 3.72Q), determinedon the 1.8659 thicker black crystalsusing heavy-liquid techniques, 840 1.8489 1.S480 agreeswell with the calculated density 3.650 g/cm3. 750 1.8001 1.8003 L.79L2 Chestermanitehas a Mohs hardnessof 6 and is brit- 1.7905 L.7227 L.7229 9 tle. It has no observable cleavageor parting, but 940 1.7100 1.7093 9 exhibits an unevento conchoidal fracture. However, L7 both chestermaniteand the associatedmagnesian- 10.30 1.6883 aluminian ludwigite fracture much more easilyacross 1.6S64 1.6978 370 1.6S67 the crystal length than parallel to it. Relatively thin L.6654 basal splinters, useful for optical study, can be 10.40 1.ss65 1.5871 950 L.577L (60) produced easily from the ludwigite in this manner, 442 6 but chestermaniteis notably more resistant to frac- I L.5406 2 ture. The toughnessrelative to ludwigite is a diag- 040 1.5341 L.534t nostic feature of chestermanite. 1.5300 1.5300 19 ( s5) 2ao I.:I53 5 Chestermanite is nonmagnetic, nonfluorescent, 004 1.510S 1.5102 1 (55) L.4966 1.4965 13 ( 55) and is either insoluble or only very stghtly soluble L.&52 1.4840 8 in hot concentrated acids (HCl, HNO3, or oqua 2L4 L.AO2 L.4SO2 11 regia). When heatedto l000oc, the mineral shows tAll no changeand only 0.590 loss in weight. .u]-"o]."t.d h&trrg ue 1L6t€d for arr*, >:.Soo i.

The optical propefiies of chestermanitewere deter- 2sg*tm 8o-pP-2. x-ray *r{..*"a-* ** lto. x46371 mined on X-ray-oriented single sryslals using a Clrxa, radlati@ (l-1.540598 i) I St tntenal etadedr Supper* spindle stage as well as on crushed grains sca!fi€d at L/go 29 E& Ehut€ tr@i5 to 1280,20. *L9latlre lntdnEltLes l! lE@tbeseg ue 6trc!966t re- *Use of trade names in this report is for descriptive pur- fL@tL@6 @rued l! a eiclod@slt@t@ tra@ of a poses only and does not imply Debleschsrc f!.lo (!1o..1052) I strtr@e @Bt of clush€d endorsementby the U.S. allgle orystaL ftu 6lel.@ 8G-PP-2' clrRo radiati@ Geological Survey. (l-1.5419 A) r rcre dlseteFll4.6 @. 914 TIIE CANADIAN MINERALOCIST

M 2. @!trca! coiodmct| 0F clBscwrE CHEMICALCOMPOSrrION

retght !o. of Standard 3.8-cm-diameter bakelite polished sec- c catl@a prepared mar- ar2% 5.3 0.20 tions were of chestermanite-bearing e:or 16.0 0.3€ ble (specimenS0-PP-2) and of acid-insoluble (HCl) $2os lo.3 o.ul residues.An ARL-SEMQ mictoprobe with six auto- rr% o.8 0.02 mated wavelength-dispersivespectrometers was used !@ 48.0 2.24 for the determination of tle composition of chester- lioo 0.t manite. Operating conditions were: 15 kV acceler- &o 0.t potential, nA sample current on brass, Bzoi' L8.22 1.00 ating l0 o.l o.ol 40-second sount times on peak positions and tsotal, 8.92 4-secondsount times on background positions for ---9:91. standards and samples. Lines used were FeKa, , 94.88 CaKa, MnKa, Ti/(> Y green, and Z brown; material. A semiquantitative six-stepspectrographic (0.09) (0.11). in parentleses f >Z The values analysis (Nancy M. Conklin, U.S.G.S., analyst) (in mm) representthe approximate crystal thickness showsthe boron concentrationto be >10 wt.9o. sensibly at which the optioal direction becomes The analysis, with the number of cations calcu- Thesevalues were ddtermined opaquefor white light. lated on the basis of one boron atom, yields the on the spindle sfage. on the'X-ray-oriented crystals formula: The opacity of X along the acute bisectrix (Z) precludesdetermination of the axial angle or of the Mgr(Fe3olrMge.2sAle.26Sb50lzTio.or)r *,Mg,Al,Sbit.ooPOs(O * r.ss dispersion. The 2V" calculated for the holotype Fo.or)zz.oor, ideally, Mgr(Fd )BO3O2. specimenis 63o. The indices of refraction, low , and DISCUSSION absorption schemeof chestermanite are closest to those of warwickite (and somewhatless sloseto thos€ Chestermaniteshows both strong similarities with, of azoproite) of the pinakiolite-ludwigite group, but and distinct differences from, the other membersof chestermanitediffers from tlese minerals in its opti- the ludwigite-pinakiolite group of minerals (hereafter cal orientation and pleochroism. The absorption abbreviated as "L-P"; seesummary by Durl et al. schemeis the easiestmeans of distinguishingchester- 1983) in its chemical, crystallographic, and optical manite from the closely associated magnesian- properties. A brief discussion of these properties aluminian ludwigite, which has X (0.04) > Z (0.06) seemsworthwhile at this point, although final reso- >> r (0.17). lution of some questions must await determination Calculation of the compatibility of the optical' of the of the mineral. chemical, and specific gravity data using the Chemically, chestermaniteis distineuishedby hav- Gladstone-Dalerelationship (Mandarino 1981)yields ing the highest content of Mg of any of the L-P a Kp of 0.211and a Ks of 0.218,and a compatibil- group; only azoproite (Konev 1978) approaches ity index of +0.32. This value indicates excellent chestermanite in this respect. Chestermanite has agreementbetween the physical and chemical data. nearly the samecontent of Sb as an unnamed mem- CIIESTERMANITE, A MEMBER OF THE LUDWIGTTE-PINAKIOLITE CROT'P 915 ber of the L-P group from Nordmark, Sweden RSFERENcES @unn e/ al. 1983),but is easily distinguished from this mineral by its X-ray powder-diffraction pattern. Bansuar, P.C., Locrwooo, J.P. & Luroll, P.A. The chemical composition of this unnamed mineral (1971):Geologic map of the KaiserPeak quadran- suggeststhat it may be identicalto a secondunnamed gle, cential Sierra Nevada, California. U.S. Geol. member of the L-P group recently described by Sum. Geol. Quad, Map GQ-894. Bovin el al. (1986) from Mossgruvan, Nordmark, Br,oss,F.D. (1985):Labelling refractive index curves Sweden. The Mossgruvan minslal is described as for mineral seies.Amer. Mineral. 70,428432. orthorhombic (spacegroup llznm or Pnn2), a 37.!0 (roughly 2a of chestermanite),b L2.54,and c 6.23 A. Bovm, J.-O., BaxnY,J., Tuouassot' R., NoRRESTAM, Crystallographically,chestermanitg is isostrucfural R. & FArnr, L. (1986):Crystal structure images of with orthopinakiolite, which it resemblesin having a newmineral, (Mg,Mn,Sb,Fe)2.9a8O5. Proc. XIth a subcell closely related to ludwigite and in having Cong. on Electron Microscopy (Kyoto, l98O' ferric rather than ferrous iron (Tak6uchi et aL l9f8). 1697-1698(abstr.). Optically, chestermaniteis distinguished by having (1980): the lowest.indices of refraction of any member of & O'Krrrrn,^M. Tak6uchiite,a new Lingban, Sweden.Amer. Mineral. the L-P group. warwickite oryborate from Only has indices of 65, l130-1133. refraction that approach those of the new minslal and has a further similarity in its absorption scheme; - & - (1981):Electron microscopy of oxy- however, the pleochroic colors are distinctly differ- borates.II. Intagrowtl and strucfiral defectsin syn- ent. The pleochroiccolors ofblue and greenishblue thetic crystals.Acta Cryst. Ayl, 35-42, reported for the X and I directions of aluminum- rich ludwigite @ertsev& Aleksandrov 1964)are the -, & O'Krerr, M.A. (1981a):Electron closestmatch to those of chestermaniteof any mem- microscopyof oryborales.I. Defeststructures in the pinakiolite, ber of the L-P goup. However,other specimensof minerals ludwigite,orthopinaliolite and takduchiite.Acta Cryst. A,n,28-35, aluminum-rich ludwigite do not show thesetints of blue in their pleochroism(Schaller & Vlisidis l96l). -, - & - (l98lb): Electronmicroscopy Furthermore, Pertsev& Aleksandrov gavethe opti- of oxyborates.III. On the structureof tak6uchiite. cal orientation a = Y and 6 = X, which differs from Acta Cryst. A.37,4246, that reported for other specimens of ludwigite Q,exrardet al. 1962).Chestermanite is also the most CHESTERMAN,C.W. (1942): Contact metamorphic transparent member of the group, and the asbesti- rocks of the Twin Lakes region, Fresno County, form or fibrous crystals show only moderate California.Cald, J. MinesGeol. Rep,38,A3-281. pleochroismand absorption. (1959):Ludwigite from FresnoCounty, Califor- na Geol. Soc.Amer. Bull.70, 1712-1713(abstr.). AcKNowLEDGEIyTENTS Comv, J.W. (1968): Quantitativeanalysis of thin insulating films. .0eAdvances in X-ray Analysis ll We express our thanks to Dr. Jan-Olov Bovin (J. Newkirk, G. Mallett & H. Pfeiffer, eds.).Ple- (University of Lund, Sweden) for the HRTEM num Press,New York. studies of chestermaniteand for many helpful dis- cussionsand exchangeof information; to Dr. Pete CooneR,J.J. & Trlr;ev,R.J.D. (1985):Direct observa- J. Dunn (U.S. National Museum) for furnishing a tion of the transformation of ludwigite to specimenof his unnamed mineral from Nordmark, orthopinakiolite. J. Solid StateChem. 58, 375-382, Sweden,and for the interchange of other pertinent W.B. Nuw- information and ideas;to Dr. Roger (Mass. Dupr, P.J., Pnecon,D.R., SurauoNs, & G. Burns nunv,D. (1983):Fredriksso4ite, a new memberof Inst. of Technology) for the M6ssbauerspectrum of the pinakiolite group from Lingban, Sweden.Geol. chestermanite;to Dr. Howard T. Evans, Jr. (U.S. Fdren. Stockholm Fdrh, 1l)5, 335-340. Geological Survey) for preparing a densitometer trace of the X-ray powder photograph of chester- HaunroN, W.B. (1950: Geologyof the Huntington manite and making a special intensity-scale for its Lake area, FresnoCounty, California. Cald, Div. measurement;and to Mrs. Nancy M. Conklin (U.S. Mines Geol. Spec.Rep. 6,3-25. Geological Survey) for the six-stepsemiquantitative spectrographic analysis. Helpful reviews by Drs. Kenrucr,D.M., Cnewrono,K.E. & Raroezzo,A.F. T. (u.S. (1973):Metamorphism of calcareousrocks in three Howard Evans,Jr. and Joan J. Fitzpatrick pendants roof in the Sierra Nevada,California. "f. GeologicalSurvey), John M. HughesMiami Univer- Petrology14,302-325. sity), and Donald R. Peacor (University of Michi- gan) are much appreciated. KoNnv,A.A. (1978):Les min6raux de titane et de zir- 9t6 THE CANADIAN MINERALOGIST

conium dansles skarnsdu massifalcalin de Tag6r- Mineral, Obshchest,93't3-2n (in Russ.,translation ane(Bartal, Sib6rie).Bull. Min4ral. 101,387-389. by M. Fleischer,1964).

LgoNARD,8.F., Htr.oennaNo,F.A. & VlIsus, A.C. ScHar-Len,W.T. & VttstpIs,A.C. (1961):The compo- (1962):Members of the ludwigite-vonseniteseries sition of the aluminian ludwigite from Crestmore' and their distinction from ilvaite. .fu Petrologic Catifornia. Amer. Mineral. 46' 335-339. Studies:A Volume to Honor A.F. Buddington. Geol. Soc.Anter., 523-568. TarEucnr, Y., Heoe, N., Keto, T. & Mrune, Y. (1978):Orthopinakiolite, Me2.e5O2lBO31: its crystal MeuoanrNo,J.A. (1981):The Gladstone-Dalerela- structure and relationship to pinakiolite, tionship.IV. The compatibilityconcept and its appli- Me2.qO2lBOl. Cqn. Mineral. 16' n5485, catton.Can. Mineral, 19,441450. Psnrssv, N.N. & Amrseronov, S.M. (1964):Lud- ReceivedJuly 28, 1987,revised rnanuscript accepted wigite with high eealsnl of alumina. Zap, Vses. October 25, 1987.