STUDIES of BORATE MINERAI,S (ID: X-RAY CRYSTALLOG- RAPHY of INYOITE and MEYERHOFFERITE; X-RAY and MORPHOLOGICAL CRYSTALLOGRAPHY of 2Cao-3Bzo .9H2O*

STUDIES OF BORATE MINERAI,S (ID: X-RAY CRYSTALLOG- RAPHY OF INYOITE AND MEYERHOFFERITE; X-RAY AND MORPHOLOGICAL CRYSTALLOGRAPHY OF 2CaO-3Bzo .9H2O*

C. L. Cunrsr, [/. S. GeologicalSuraey, Washington25, D. C. Ansrnacr fnyoite is monoclinic,P21/a, ao:10.63, bo:fi.A6, co:8.40rA, F:114.02,. 2CaO'3BrOa.9HzOistriclinic PT, ao: /.94, bo:9.452,co-7.412 A, a:101"21,,p-: l}l"7g,, t:99"49'. The findingsof Switzerin Palache(1938) for meyerhofferiteare confirmed. Powder patterns, partially indexed, are given for inyoite, meyerhofierite,and 2CaO.3BzOs.9HrO.

INrnooucrroN ANDAcrwowr,ooGMENTS A systematic study of borate minerals has been continued in the present investigation with the determination of the r-ray crystallography of inyoite, 2CaO.3B2OB.13H2O, the *-ray crystallographyand morphology of the synthetic mineral 2CaO.38zOs.9HzO,and the redeterminationof the r-ray crystallography of meyerhofierite, 2CaO.3BzOt. jIJzO. Results obtained on meyerhofferite were in excellent agreementwith those previ- ously reported by Switzer in Palache (1933). Powder patterns of the three compounds have been measured and partially indexed. The work was undertaken primarily as a preliminary to the determination of the structures. The writer is indebted to various colleaguesin the U. S. Geological Survey: Waldemar T. Schaller furnished the crystals studied; Mrs. Joan R. Clark made many of the calculations and film measurements; Howard T. Evans, Jr., made the goniometric measurementson and the drawing of 2CaO.3B2OB.9HsOand,also renderedmuch helpful advice; Fred A. Hildebrand prepared the powder patterns reported.

ExpBnrlrpwrAr, WoRK All of the crystals used were synthetic. Schaller (personal communica- tion) has furnished the following description of the methods of prepara- tion:

Inyoite (2:3:13). Grown on ulexite fragments placed in water and held ar room temperature for about two months. Artificial (2:3 :9) . Grown on ulexite fragments placed in water and held at 50. C. for approximately one month. Meyerhofierite (2:3:7). Grown on ulexite fragments placed in water and held at 70- 80" C. for approximately six months.

The inyoite crystals were colorless,transparent, tabular {001}, with {110} and {001} dominant, i.e., having essentiallythe habit described * Publication authorized by the Director, U. S. Geological Survey. 912 X-RAY CRYSTALLOGRAPHYOF INYOITE AND MEYERHOFFERITE 913 by Schaller (1916) for the crystals found at the original Inyo County, Calif., occurrence.The crystalsof the 2CaO.3B2OB'9HzOwere likewise colorless and transparent and are described by the drawing given in Figure 1. The crystal is flattened on {101}. In order of decreasingim- portancethe forms observedare: g {101}, a {100}, b {010}, e {011}, M {110},t {111},s {121},and I l1Z0}.The lastthree are not shownon the drawing. The morphological study shows no evidence for assigning

/vl n ,r,1 t. -trt'-/ l./\/

Frc. 1. Crystal of 2CaO 3B:Os.9H2Oof typicalhabit (Evans, 1953 personal com- munication).

Forms: b 010 e 0T1 100 o 101 M 1T0 Iessthan holohedral symmetry to the crystal. The meyerhofferitecrystals were colorless,transparent, prismatic elongated[001] with {100} dominant and {110} somewhatless dominant, i.e., having the habit given in figure 43 of Schaller'soriginal description(1916). The determination of the lattice type and the measurementsof the lattice constants were made using a qtrartz calibrated precessioncamera with Mo/Zr (X":0.71069 A; I",:9.76926 h) radiation. The precession films were corrected for vertical and horizontal shrinkage. The powder patterns were prepared in a 114.57 mm. diameter camera with Cu/Ni radiation. Shrinkage corrections were applied. The values of the axial Tenre 1. CnysrlllocnapnrcErnrmNrs or lryonr-2CaO.3BzOa. 13IIzO

Symmetry: Monoclinic; space group P2t/a(Czf)

Axial elements: ao: 10.63A A:fl4"02' bo: 12.o6 co: 8.40b a:b :c : :0. 8814: 1:0. 6969 V:984.1 AB Z:2 Density(calc.) : 1.373 9t4 C. L. CHRIST

T lrsta 2. Cnvsrer-r-ocnaprrrcEr-EMENTs ol 2CaO' 38 zOi'9H2O

Symmetry: Triclinic; space group Pl (Ci1)

Axial elements: ao: 7.04eA a:l07o2ll bo:9.452 9:r01"r9' co:6.412 'v: 99"49', a :b:c:0. 7455:7 :0.67 84

Polar elements: a*:0. 1483 \.:76o13' b*:0.1106 p:76o74' c*:0.1638 v:77"26' Po:qo:16:0.9055 :0. 6751 : 1

Projectionelements: xo':0.2001 po':0.9508 Yo':0.2502 qo':0.7089 v:77"26'

Cartesianmatrices: vr- -0.2133 vs:0.9570

Direct: ll o.ooo-2.016 o ii M: ll o e.o4s o ll (i"A) ll -1.383 -1.860 6.4r2 ll

Reciprocal:

V:r+00.7Aa Z:1 density(calc.):2.002 lengths for inyoite and meyerhofferite are believed to be correct to 1.5 parts per 1000. The intervector anglesare accurate to approximately 05'.

RBsurrs The results obtained from the #-ray single crystal study of inyoite are given in Table 1. The ratio of the axial elements and the value of the B-angleobtained in the r-ray work for inyoite are in excellent agreement with those obtained from morphological studies by Poitevin and EIls- worth (1921): Presentwork a:b: c:0.8814: 1 :0.6969 F:714'02' Poitevinand Ellsworth a:b: c:0.8833: 1 :0.6950 A:114"01' X.RAY CRYSTALLOGRAPHYOF INYOITE AND MEYERHOFFERITE 915

The value of the r-ray density is 1.873.Schaller (1916) obtained 1.875 by the suspensionmethod on Inyo material. The crystallographic elements obtained from the r-ray work on 2CaO'3BzOe'9HrO are collected in Table 2. The formulas given by Evans (1948) were used in the calculations. The specifi.cgravity of this compound was determined on the Berman balance to be 2.00. This value agreeswell with the r-ray value of 2.002.

Tnern3. ColpemsoNol X-nevRnsur.rs ron INvorra,2CaO'3BzOa'9EtzO, MrvnrrrorlnurE, ANDCornuaNrrn

Mineral Inyoite Artificial Meyuhofierite* Colerooite**

composition 2cao' 3Bzor'l3Hzo 2cao' 3B,or'9H'o 2cao'3Bros'THro 2cao' 3B'or'5H'O

Monoclinic Monoclinic

Space Group P2,/a (C,f) PI (Cir) PI (C;) Pz,f a (C,al)

a 10.63A 7.046A 6.61A 8.743 a b 12.06 9.45, 6..tJ 11.26+ c 8.40, 6.412 6.49 6.102

(e0'00) t0t"2ll 90"ocr (e0'00) t14'O2', 101'1g'. 101'31' 110"07' a (e0'00) 99"49', 86'55' (e0"00)

Volume 984.1A3 400 7 A3 350.5 A3 sa+.2it" density (calc.) 1.873 2 002 2.tt8 2.4r9 a:b:c: (r-rays) 0 8814:1:0.6969 0.7455:1:0.6784 O.792:1:O.777 0.7762:\:O.5418 Vol /0-atom 20.5 A3 20.0A3 19.s A3 17.6A3

* Switzer in Palache(19J8) (original kX units convertedto A). ** Christ (1953).

The present study completesthe determination of the crystallographic elementsof the known membersof the series:2CaO'3BzOr'xHzO, where x:13, 9, 7, and.S.The pertinent data on the four membersof the series are collected in Table 3. One of the most interesting results of this com- parison is that there is a progressivedecrease in the volume occupied per oxygen atom with decreasingwater content. In the caseof colemanite the 17.6 At per oxygen atom is about the value expected if the structure is determined by the nearly close-packingof oxygen atoms (Christ, 1953)' It is apparent that in the higher hydrates the percentageof oxygen atoms in nearly close-packing decreases.It is planned to study the thermal analysis for this seriesas an aid, and in addition, to the structural analysis. The partially indexedpowder patternsfor inyoite, 2CaO' 3BrOa'9HsO, and rneyerhofferite are given in Tables 4 to 6. Tesrn 4. X-nnv Pomnn Dare: Ixvorrr-2CaO.3BrOr.13HrO MonoclinicP21 / a; as: lQ.(3, bo: 12.06, c0: 8. 405A, P: 174'02'

Measured* Calculated

Cu/Ni I:1.5418A

dnrr hkl

71 /.Jv / . .)Gt 110 6 5.98 6.030 020 (+.t+s 2lr 18 4.72 14.74s 021 l.4.6e5 111 13 3.85 3.841 002 9 3.7r 13.714 130 13.690 212 4 3.45 3.449 r22 6 3.37 3.369 2:J,1 6 3.13 3.126 310 3.033 22r 100 3.03 J t3.ols 040 203 13 2.775 12.77e lJ 177 032 9 2.643 2.643 23r (z.sos o13,332 18 2.494 lz.+o+ 212 l2.483 132 J 2.41O 2.406 321 24r 25 2.286 zJa 133 410 25r,422 4 2.185 I 2.181 142 151 204 13 2.098 r52 420 431 9 2.049 252 233,052 6 1.972 13 1.916 18 1.880 1.752 i 1.605 6 1.528 6 1.441 Plus additional weak lines.

* Shrinkage correction negligible. X-RAY CRYSTALLOGRAPHY OF INYOITE AND MEVERHOFFERITE 917

Tasr,E5. X-nev Powort D.lra: 2CaO'3BsOs-9HrO TricfinicPf ; as:7.040,bo:9.452, co:6.412 A a: l}l"2l', I : l0lo 19', 7 :99"49'

Measured* Calculated

CulNi r: 1.5418 A

d*t d*t

100 9.14 9.05 010 100 o. /J o. /4J 100 4 6.08 6.079 T10 .1./o 5.7sr 011 50 5.20 5. 181 T01 6 4.88 4.916 110 50 4.56 4.564 II1 120 7r 4.r9 [+.zoz t4.19s 111 13 4.07 4.070 101 25 3.59 .J-56/ 12r 18 3.36 3.364 111 IJ 3.14 35 308 50 3.O2 18 2.966 18 2.864 5U 2.807 25 2.700 9 2.594 ll 2.573

IJ 2.463 4 2.405 o 2.369 IJ 2.333 13 2.268 i 2.228 18 2.r57 9 2.t33 2.t04 IJ 2.048 9 2.005 9 r.940 9 r.911 9 1.878

Plus additional weak lines.

* Shrinkage correction negligible. 918 C. L. CERIST

Tanro 6. X-nav Poworn Dera: MevBnnollnmrr-2Cao.3BzOB. THzO TriclinicPf; a6:f .61,bo:8.35, co:6.49 A* a :91'00', A: fif 3l', ry:86'55,

Measured*x Calculated

Cu/Ni \:1.54134

d*r du hkl

100 8.39 8.33 010 100 6.51 Ia.+o 001 \6.47 100 50 5.03 5.038 011 8 I 11 [+.roz 020 l4.r4r 101 18 3.65 s.670 1T1 12 3.50 35 3.30 100 3.r7 18 3.09 18 2.974 nil 2.900 18 2.641 50 2.540 50 2.520 4 2.463 25 2.149 18 2.093 18' 2.072 18 2.019 18 1.988 18 1.956 18 1.928 18 1.894

Plus additional weak lines.

* Original units in kX. Given here in A. Error*0.02 A. *x Shrinkagecorrection negligible.

Rrlprurcns crnrsr, c. L. (1953),studies of borate minerals: r *-ray crystallography of colemanite: Am. Mineral.,38, 411-415. Evaus, H. T., Jn. (1948),Relations among the crystallographicelements: Am. Mi,neral,., 33, 60-63. Per,ecnt, C. (1938),Crystallography of meyerhofierite:Am. Mi,nual.,29, fu-64g. Pot..rvr*, E., ^*o Br,Lswonru, H. V. (f921),-fnyoite from New Brunswick: Geol. Swvey Canaila,Bull., 32. Scnarrnn, W. T. (1916), Inyoite and meyerhofferite,two new calcium borates: [/. ,S. Geol.Suntey Bull., 610, 3S-SS.