Canadian Mineralogist Vol. 21, pp. 29-35(1983)

WADSLEYITE,NATURAL F-(Mg, Fe).SiOnFROM THE PEACERIVEH METEORITE

G. D. PRICE, A. PUTNIS eNp S. O. AGRELL Departmentof Earth Sciettces,University ol Cambridge,Cambridge CB2 3EQ, England

D. G. W. SMITH Departmentof Geology,University of Alberta, Edmonton,Alberta T6G 2E3

ABsrRAcr tion 6lectroniquesont compatiblesavec le groupe spatialImma. La nouvelleespdce honore feu le Dr. Wadsleyite, a new mineral species, occurs as a A.D. WadsleST'. fine-grained material in fragments within a vein (Iraduit par la R6daction) in the Peace River meteorite (Alberta); it was formed by a series of polymorphic phase trans- Mots clds: wadsleyite,nouvelle espdce,F-(MeFe)z formations, from olivine and ringwoodite, during SiOr,polymorphe, min6ral du manteau,m6t6orite, (Alberta). an extraterrestrial shock event. Wadslevite has the 6v6nementde choc, PeaceRiver structure of the P-phase polymorph of (IvIg,Fe)cSiOr and an ideal composition of (Mg,."Feo.JSiOo.Single INtnoouctIox crystals of wadsleyite rarely exceed 5 p,m in dia- meter; polycrystalline aggregates are transparent Wadsleyite, a new mineral species found in with a pale fawn coloration and a bulk index of the Peace River meteorite (Alberta), is the refraction of 1.76. The strongest six reflections in naturally occurring B-phase polymorph of (Mg, the X-ray powder-diffracrion pattern td in A qy Fe)rSiO.. The occurrence of the p-phase as an (/r A l)l are: 2.89(m) (040), 2.69(m) (013), 2.45(s) intermediate in the high-pressuretransformation (lal), 2.04(s) (240), r.57(m) (303), L4aG) Qa{. of magnesium-rich olivine to its spinel-structure Wadsleyite is orthorhombic with a 5.70(2), b ll.Sl polymorph was first reported Ringwood (7), c 8.24(4) L, V Slt(l) ]r", Z- 8 and. on the by & basis of the ideal formula, has a calculated density Major (1966). The B-phase was subsequently of 3.84 g cm-3. All observed X-ray and electron- confirmed to have a stability field by Akimoto diffraction data are compatible with space group & Sato (1968),Akimoto (1970) and others,who Imma. The new species is named after the late performed further studies on the system (Mg, Dr. A. D. Wadsley. Fe)$iOa and also synthesizedisostructural ana- logues with compositions CozSiOa, MnrGeO4, Keywords: wadsleyite, new mineral species, F-(Ms, Ni,,AlrSiO' Fe)rSiO., polymorph, mantle mineral, shock and ZnzSiO". event, meteorite, Peace River (Alberta). Phase equilibria in the solid-solution series MgrSiO'-FerSiOo have been widely studied be- Souuernr cause the polymorphic phase transformations in this series are believed to determine directly the La wadsleyite, espdce nouvelle, se pr6sente en structure of the earth's mantle. In particular, the mat6riau finement grenu dans des fragments i polymorph of (Mg,Fe)zSiOais expected peacE li-phase l'int6rieur d'un filon dans la m6t6orite de to comprise a significant proportion of the River (Alberta). Elle s'est formde par transforma- transition zone of the mantle. Obviously, since tions polymorphiques, i partir d'olivine et de no mantle-derivedp-phase is ringwoodite lors d'un dv6nement-chocextraterrestre. available,the study La structure est du type g-(Mg,Fe)2SiOr, avec of this compound has previously been restricted (Mg,."Feo.5)SiOo comme composition id6ale. Ies to synthetic material. The discovery of wads- monocristaux excident rarement 5 um de diamdtre: leyite in the PeaceRiver meteorite is particularly les agr6gats polycristallins sont transparents et pos- important, therefore, because of the further sadent une faible coloration fauve et un indice insight into the behavior of this mantle-forming de r6fraction moyen de 1.76. I-es raies les plus material that can be obtained by studying the intenses du ctich6 de pondre [d en A(tXlr & /)] sont: naturally produced 2.89(m) (040), 2.69(m) (013), 2.4s(s) (l4l), 2.04(s) B-phase. It was originally proposed by Ringwood & (240), 1.57(m) (303), La4G) Q44. La wadsleyite est orthorhombique avec a 5.70Q), b ll.5l(7), Major (1970, p. 107) that if p-(Mg,Fe),SiO, c 8.24(41 4,, V SqtQ) A" pour Z - 8; sa densit6 were ever to be found in nature, it should be calcul6e ir partir de la formule id6ale est de 3.84. named wadsleyitein honor of the late Dr. A. D. Toutes les donlr6es de diffraction X et de diffrac- Wadsley, "whose outstanding crystallographic 29 THE CANADIAN MINERALOGIST

left and right of the Hc. l. A. Typical vein-structure in the Peace River meteorite. The light areas to the The opaque vein-material vein are recrystallized chondrite of which the meteoriie is largely composed. phases. rounded fragments is made up of sulfide *O -"t"f aroplets and microcrystalline silicate The WADSLEYITE FROM THE PEACE RIVER METEORITE 31

investigations in minerals and inorganic com- by transmission electron microscopy (TEM). pounds are renowned to all within his field and The polycrystalline aggregates of wadsleyite to many outside". We endorse this proposal, have a felsitic texture and are invariablv fras- which has also been approved by the Commission tured. They are transparent and have a pale on New Minerals and Mineral Names of the fawn coloration. By virtue of the small crystal- International Mineralogical Association. The size,no detailedoptical data on wadsleyitecould type specimen is preserved in the collection of be obtained;however, the grains are anisotropic the Department of Geology, University of and show low, first-order birefringence colors. Alberta. Relatively large wadsleyiteaggregates have,'an effective index of refraction of 1.76. This com- OccunnnNcn AND AppEARANcE pareswell with the valueof 1.77 calculatedfrom the Gladstone-Dale mle (Mandarino 19j6, . Wadsleyite has been found in the L6 hyper- 1978, 1979). sthene-olivine peace chondritic River meteorire, TEM shows that wadsleyite polycrystalline the fall and recovery of which have been des- aggregatesare generally composed of well- cribed by Folinsbee & Bayrock (1964). The formed gralns, with intergranular boundaries PeaceRiver meteorite is distinctly recrystallized, usually meeting at triple points (often with and has only a poorly preserved chondritic interfacial anglesclose to 120"). In addition to structure. The meteorite is largely an assem_ wadsleyite, the fragments may contain small blage of olivine, orthopyroxene, plagioclase, amounts of majorite or microcrystallineaggre- iron-rqickel alloys and troilite. plagioglase ThO gates of pyroxene pseudomorphing majorite has.beenextensively converted to its amorphous (Price et al.1979) and highly faulted ring- equivalent,maskelynite, which indicates thit the woodite. Wadsleyite is also occasionally found meteorite has been subjected to a high-pressure to carry stacking faults, which predominantly shock event. In addition to this shock-produced lie on.(010) (Fig. lC). Thesemay be viewedas phase, the Peace River meteorite contains thin, Frank-type faults, corresponding to the removal black, sulfide-rich veins, which pervade the body of a stoichiometric (Mg,Fe)zSiO*layer accom- of the specimen in much the same wav as veins panied by a V+[OIO]displacementn and are inter- found in other meteorites believed to have preted as being structural mistakes incurred undergone an extraterrestrial shock event [e.g., during the relatively rapid, post-shock growth Tenham, Coorara, Catherwood and Coolamon: process. Price et al. (1979)1. Typically, within rounded fragmentsfound in theseveins, the constituent Cnrurcel AND SrRucrunel .Dere grains of olivine and orthopyroxene have been transformed into their high-density polymorphs, Electron-microprobedata for olivine, wads- the spinel-structure ringwoodite and the garnet- leyite and the other major, nonmetallic phases structuremajorite, respectively(e.S,., Binns 1970, found in the PeaceRiver meteoriteare given in Price et al. 1979), The vein studied in the peace Table I, and their recalculatedstnrctural for- River meteorite differs significantly from those mulae in Table 2. The analyseswere performed described in other meteorites. however. in that using an ARL EMX microprobe fitted with it containssignificant quantities of wadsleyite. three wavelength-dispersionspectronleters and The wadsleyite occurs as microcrystalline an Ortec energy-dispersionspectrometer. Well- ageregatesthat pseudomorphpreviously existing characterized analytical standards were used olivine fragments within the vein (Figs. lA, B,t. throughout. All data were obtained at an oper- The wadsleyite-bearingfragments rarely exceed ating voltage of 15 kV and with probe currents 0.5 mm in diameter, and the actual grain-size of the order of 20 nA. Wavelength-dispersion of the crystals within the polycrystallinefrag- results were processed using ApL program ments is between 0.5 and 5 prn, as estimated PROBEDATA (Smith & Tomlinson 1970), and

within the vein are largely composed of shocked olivine and its high-density polymorphs, wadsleyite and ringwoodite. B. An enlarged view of a wadsleyite-bearing fragrient surioundid Uy vein material. The.fragment is made up of microcrystaltine wadsleyite (W) and shoiked olivine (o). the"devetopment of tracturing is common. C. Transmission electron micrograph of wadsleyite, showing stacking faults developed normal to (010). The faults have a displacemint of %tol}). These faults occui in the wadsleyite because of the relatively rapid, post-shock grcwth pro".... tj. Electron micrograp6- of a fault-free wadsleyite OV)_grai1 _topoJacticallyreplacing highly faulted ringwoodite (R). The i*o ptru... are related such that [010]rr ll [ll0Jn and [001]s li [001]n. 32 THE CANADIAN MINERALOGIST

TIA'JE I. @SFOSTTIO}€ OF DIiAIJZED PEASESDI GE PEACERIVER I,GIEORIIE

.r&toErla t orirvtNE TADSI,EIttE t&l-ca PYRot@!{E glcg-ca FgRogE b.of * lo 9 hal. Er . AV I{t AV ET IO AV Bt tO AV EI I,o AVSIrc El

F ot /to.82 40.91 40.74 40.91 41.06 40.81 44.& 44.72 44.38 43.@ 43.79 43.52 44.25 44.7L 43.46 Na o.17 0.17 0.o Itg 23.13 23.29 22.99 23.Os 21.53 22.74 17.26 17.51 r7.03 ro.l9 10.56 lo.o5 l?.79 18.59 17.3s Al o.o3 0.o? o.o o.o9 o.t4 0.o o.28 0.33 0.21 0.06 0.o8 0.o s1 L7.47 L7.9i L1.76 18.08 1e.25 17.97 25.97 26.2L 25.53 25.27 25.& 25.16 25.24 26.o5 23.73

c1 a Ca O.Ol 0.06 O.O o.o5 0.ll o.o o.53 0.?o o.41 15.42 15.82 15.10 o.42 0.57 0.28 Tl O.O O.O O.O o.o9 0.L2 0.o o.25 0.27 0.2L o.lo o.ll o.o9

Cr O.O O.O O.O o.ol o.o7 0.o o.o9 0.2L o,o o.58 0.69 0.48 o.l3 0.23 0.o8 Mn o.37 O.43 O.32 o.33 0.36 0.31 o.38 0.41 o.33 o.r5 0.L8 0.L2 o.3? o.41 0.33 F€ 17.67 17.SO L7.43 r?.39 l?.78 16.73 1o.95 lt.57 10.71 4. 05 '1.43 3.45 11.60 13.26 ro.52

Nt o.o4 0.o8 0.o o.@ o.l3 0.o7 0.oI o.oa o.o o.ol o.oa o.o o.o2 0.o7 0.o 7a o.oa o.L2 0.o o.o8 o.l9 0.o o.o3 0.1I o.o o.o3 0.11 0.o o.o3 0.o8 0.o TOrAr. loo.@ (.rOO.36t 1@.@ ([email protected]) l@.@ ([email protected]) 100.@ ([email protected]) 100.oo ('98.3S)

I PIAGIOCTiSE ctnoulrE ,rrr"t oI IERRIInIIts - APA[tlE' No. of lO T2 6 2 Anal' Av gr ro AV Sr rt AV EI IO AV IJ IO Hi o.o7 0.19 o.o o.o4 0.o8 0.o o.37 0.40 0.34 1.Ol 1.O5 0.97 ot 48.tI 4g.tB 49.o2 30.20 30.22 30.16 32.06 32.15 31.97 4L.73 42.LL 4I.49 37.44 17.57 37.16 Na ?.o3 ?.14 6.0g 1.98 2.& t.8l o.38 0.40 0.36 !r9 o.23 o.4I o.io 1.88 2.6 L.12 r.75 r.8S r.61 2.36 2.49 2,29 o.39 0.39 0.39 A1 lo.9g 11.05 10.82 3.15 3.30 3.@ o.1l o.I4 0.o9 o.15 0.17 0.13 si 30.48 30.55 30.38 o.44 0.54 0.40 0.26 0.35 0.18 o.24 0.32 0.18 o.30 0.35 0.25 P 19.73 19.S 19.40 17.65 17.69 17.65

5.Ol' 5.20 4.83 R O.90 2.o4 0.56 ca l.60 1.So L.44 o.o2 0.12 0.o o.& o.o4 0.o3 32.69 32.93 12.L7 rt o.o o.o o.o L.77 1.90 1.59 h.62 3L.29 29.96 o.40 0.46 0.36 cr 36.88 37.26 35.oS o.l7 0.24 o.o5 lln O.Ol 0.6 O.O 0.36 l.o4 0.1? o.95 l.o3 0.97 o.o8 0.18 0.o o.o4 0.o9 0.o Fa 0.65 o.73 O.58 24.54 25.& 24.27 34.14 34.50 33.78 0.65 0.9? O.40 o.22 0.26 0.18 Co Nl o.o2 0.o3 0.ol 7e o.32 0.42 0.26 TOTA!, IOO.OO (rhO.O7) [email protected] (.loo.o9) [email protected] (r99.o9! l@.@ (rlo.o5) l@.@ (.100.08)

calqulrtsal tl fuo EAO by dl!!.tanc. lrcE l@i r Orlgbd tolalr trcE rhlch udy$! hlvo b66n r€crlcul.tetl faretonftn aIlrtnrstE Atl othc! I udytl! usd tor [email protected] 6d lor F, st & Fe on otLtt?o eal @rrllltt.. d.telulutlq! bV .erltballttf,n1.! erlyrls, tlo calcuht il throughout WADSLEYITE FROM THE PEACE RIVER METEORITE 33

TNALE 2. SIRT'EN'RAL FONXUIAE OF PEASES IN PEACE NrVER UE'FEORITE

otx\tINE llN)StEtrtE rrn-ca tXGH-Ca IAJORITE PIAGIOCIASE CEROIIIIE II.}IEMTE IIERRI!'rITA APATIIE PIIOXENE PCnO!G!|E

r.4526 0.2158 F 0.4158 0.2731 o 4.@ 4.o@o 6.o00 5.qroo 6.0@0 8.OOOO 32.oooo 3.m@ 56.5244 L2.O326 Na o.o.r@ o.732L 1.8520 0.os53 us 1,4931 L-4A26 L.s271 0.9222 1.587L o.o247 L.3774 0.1075 2.LO36 0.0814 Al o.@L6 0.oo7t o.0,226 o.@51 1.0830 1.9760 0.0908 0.0289 st 0.9978 1.@69 L.9905 1.9809 r-.9488 2.Aa77 0.2655 0.ol4l 0.1878 0.0551 P 13.8016 2.93L9 s cl o..1269 x o.0614 Ca o.@18 o.o285 0.a472 0.0299 o.to64 o.o1@ o.@13 L7.6723 4.794L Tt o.@40 0.oII4 0.@45 0.6256 0.957L v o. 133t Cr o.@u o.@4 o,(D37 0.0245 0.@53 L2.O2& O.@49 tb o.olo5 o.oo95 o.ol49 0.@6() 0.0145 o.@2 o.l.Io8 0.0258 o.o3@ o.@35 Fe o.49@ o.4A7L 0.4420 0.1597 0.4514 o.o3lo 7.4622 0.9153 0.2518 0.o2o.2 Co

TT o.@lI o.@24 0.605 0.@o3 0.@a o.0006 7a o.@tl o.@20 o.ooll o.@11 o,m8 o.gr24

energy-dispersionspectra by EDATA (Smith & Compositions given also are for the'apatite plagioclase, Gold 1976) or EDATA2 (Smith & Gold 1979). chromite, ilmenite, merrillite, and 'majorite' Analysis of five polycrystalline wadsleyite (or retrograded majorite) found in fragmentsgave an ideal formula of Mgr.sFeo.sSiOr. the meteorite. This composition is more iron-rich than that Wadsleyite-containing fragments were hand- of previously reported synthetic lj-(Mg,Fe)rSiO6 picked from the vein in the Peace River meteor- and the observed wadsleyite may represent a ite, and an X-ray powder pattern was obtained metastable extension of the B-phase field. Un- with a 114.6-mm-diameterGandolfi camera. transformed olivine in the body of the meteorite Owing to the fine-grainednature of the material, was found to have the same composition (within the diffraction peakswere necessarilybroadened. experimental limits) as the wadsleyite (Iable l). Nevertheless,the sample yielded twelve well- The similarity in composition between these two defined powder lines Clable 3) that were all polymorphs is consistentwith the nonequilib- indexedin terms of the known B-phasestructure rium, shock-inducednature of the transformation (Moore & Smith 1970). A least-squaresrefine- involved in the formation of the high-density ment of the wadsleyite X-ray data"gave cell- (Mg,Fe):SiOn phase.By analogywith ringwoodite, parameter values for the orthorhombic lattice df the spinel polymorph of (Mg,Fe):SiOa,it is sug- a 5.7O(2), b ll.sl?) and c 8.24(g A. ttre gested that the name wadsleyite should apply calculated cell-volume of wadsleyite is 541(3) to all specimenswith the B-phase structure in A', and with Z = 8, the calculatid density, on the system MgzSiOa-Fe:SiOa,in which Mg;Fe. the basisof the idealizedformula, is 3.84 g cm-'. The compositions of the low- and high{a A recent structure determination of the syn- pyroxenes found in the body of the meteorite thetic p-MgzSiOr polymorph (Horiuchi & Sawa- presented also are in Table l. TEM reveals thar moto 1981) has confirmed that B-MgrSiOohas adjacent to the shock-producedveins; thb low-Ca the Imma space group and cell parametersd pyroxenes occur both in monoclinic and ortho- 5.698, b 11.438,c 8.257 A. Differencesbetween rhombic forms. The monoclinic polymorph these data and those obtained for wadsleyite are invariably exhibits polysynthetic twinning, sug- explainable in terms of the differing composi- gesting that it has inverted from an earlier tions of the phasesand the relat'iveprecision of protopyroxene structure (cl. Price et al. 1979). the trvo setsof data. 34 THE CANADIAN MINERALOGIST

TAaLE 3. X-RAY PO|DER-DIFFRACTION DtrTA I,IOB TSBDSIJYIITT AND SYNIEEjrIC B-Uq2S1O4

WADSI.EYI'IEt B-ngrstoa dc hkl I do dc !"k I I" do

20 3. r95 3.208 LL2 40 3.26 3.207 I r 2 () 50 2.48,6 2.877 o40 20 2.855 2.85L O 4 40 2.69L 2.673 oI3 40 2.677 2.673 0 L 3 30 2.637 2.623 2lr 50 2.622 2.62L 2 L L l5 2.583 2.553 220 5 2.556 2.550 2 2 0 I@ 2.452 2.452 t4t 1@ 2.437 2.442 I 4 I 80 2.o38 2.O25 24() 1@ 2.o19 2.or8 2 4 0 t5 L.872 1.876 r43 Lo 1.875 L.872 I 4 3 20 L.670 1.670 204 I5 L.6'IL 1.673 2 0 4 30 1.567 r.563 303 10 L.562 L.562 3 0 3 30 r.552 1.557 341 20 1.5c4 1.554 3 4 I 80 L.442 L.444 244 l@ L.444 L.442 2 4 4

cuKo radlatlon, Ni f,lltered; potycrystalllne f,raguent, I14'6m Gandolfi ca$era' t grotE' I@a' intensitLes estlmated vlsuallyl indlces based on an orthorhoDblc cellr sPace

r Data taken from ltoore & snlth (I97o)

PenecENnsts to dependon the time scaleover which it occurs. In the Tenham meteorite (Putnis & Price 1979' The occurrence of wadsleyite in the Peace Price et al. 1979), the thermal event was River meteorite should be interpreted in terms relatively short, and little reversion to lower- of a general sequenceof transformations, both density'phases occurred. Thus, for example, prograde and retrograde, during a shock event. majorite is found only partly retrograded to- a In the prograde sequence, high-density phases microcrystalline aggregate of pyroxene. The are formed in veins that have resulted from pressure release causes stacking faults of, the the interaction of shock-wave fronts passing type Vetl l0l (110) to form in ringwoodite;these irregularly through the polycrystalline parent locally produce the cation distribution of wads- body (Frederiksson et al, 1963). Within these leyite in the plane of the fault. veins, olivine is transformed to ringwoodite and pyroxene to majorite; both have apparently The PeaceRiver meteoriteshows evidqnce,of nucleatedfrom a high-densityglassy phase (Price a longer retrograde event.The majorite is almost et al.1979). There is no evidenceto suggestthat totally transformed to microcrystalline pyroxene, wadsleyite forms as an intermediate between and the ringwoodite,where still preserved,has olivine and ringwoodite in this prograde a very high density of stacking faults. Within sequence. these highly faulted regions,wadsleyite (Fig. 1D) The retrogtade sequence is the result of a is able to nucleate and topotactically replace post-shock thermal event (Sttiffler 1972). A de' the ringwoodite(Price et al.1982). This sequence crease in pressure coincides with a temperature representsan example of a kinetically controlled increase,enabling lower-densityphases to replace transformation, in which wadsleyite is formed those formed during the peak pressure of the as an intermediatebetween ringwoodite and the shock. The effect of this thermal event apPears ultimately stable,low-density olivine polymorph. WADSLEYITE FROM TIIE PEACE RIVER METEORITE 35

ACKNowLEDGEMENTs Moonr, P.B. & Srurrn J.V. (1970): Crystal structure of 9-MgrSiOa.Phys. Earrh Planet. Int.3. The authors acknowledge the kind help of 166-177. Dr. A. Kato (Chairman of the Commission on PRrcE, G.D., PurNrs, A. & Acnill, S.O. (1979): New Minerals and Mineral Names. I.M.A.) Electron petrography of shock-produced veins in and Dr. J. D. C. McConnell. We also thank the the Tenham chondrite. Contr. Mineral, petology Natural Environment Research Council for 71, 2lt-218. providing the electron microscope facilities used -, & Surru, D.G.W. (1982): A spinel in this study. G. D. Price gratefully acknowl- to 9-phase transformation mechanism in (Mg,Fe), ,edges the receipt of Research Fellowships from SiOo. Nature 296, 729-731. N.E.R.C. and Clare College, Cambridge. PurNrs, A. & Pnlcr, G.D. (1979): High pressure (Mg,Fe)rSiO, phases in the Tenham chondritic REnnneNcrs meteorite. Natute 280, 217-218.

RtNcwooo, A.E. & Me.ron, A. (1966): Synthesisof Axtuoro, S. (1970): High-pressure synthesis of a Mg2SiOa-Fe2SiOo spinel solid solutions. "modified" spinel and some geophysical Eartlt implica- Planet. Sci. Lett. 1. 241-245. tions. Pftys. Earth Planet. Int. B, 189-195. & - (1970): The sysrem MgrSiOo- & Sero, Y. (1968): High-pressuretransfor- at high pressuresand temperatures. p/rys. mations in Co2SiOoolivine and some geophysical IOSIO4 Earth Planet. lrrt. 3, 89-108 implications. Phys. Earth Planet. Int. l, 498-504. Snrrs, D.G.W. & Goro, G.M. (1976): A scheme BrNNs, R.A. (1970): (Mg,Fe)rSiOo spinel in a for fully quantitative energy dispersive meteorite. Phys- Earth Planet. Int. B, 157-160. micro- probe analysis. Advances X-ray Anal. lg, 191- FoLTNSBEE,R.E. & Beynocr, L.A. (1964): The, peace 2Ar. River meteorite: fall and recovery. Roy. Astron. & -=- (1979): Soc. Can. 1.58. 109-t24. EDATA2: a FORTRAN IV computer program for processing wavelength- FREDERTKsSoN,K., DE CARLT,p.S. & Alnalvrer, A. and/or energy-dispersive electron microprobe (1963): Shock induced veins in chondrites. /n analyses. Microbeant Anal. Soc. proc., I4th Arut. Space Research III (W. Priester" ed.) North- Corl. (San Anronio) (D.E. Newbury, ed,.), 273- Holland Publ., Amsterdam, The Netherlands. 278. Honruorr, H. & Seweuoro, H. (19g1): g-MgzSiOr: & TourrNsoN, M.C. 0970): pROBEDATA: single crystal X-ray diffraction study, Amer. an APL language program for use in electron Mineral. 66, 568-575. microprobe analysis. State Geol. Surv./IJniv. Kansas, Cotttp. Contr. 45. Merpanrno, J.A. (1976): The Gladstone-Dale rela- tionship. l. Derivation of new constants. Car?. Srdrprrn, D. (1972): Deformation and transforma- Mineral.14, 498-502. tion of rock-forming minerals by natural and experimental shock processes: I. Behaviour of (1978): The Gladstone-Dale relationship. minerals under shock compression. Fortschr. II. Trends among constants. Carr. Mineral. 16. Mineral. 49. 50-113. 169-174.

--- - (1979): The Gladstone-Dale relationship. III. Some general applications. Can. Mineral. li, Received May 12, 1982, revised manuscript accepted 7t-76. August 5, 1982.