The Mordenite-Ptilolite Group; Clinoptilo- Lite, a New Species

THE MORDENITE-PTILOLITE GROUP; CLINOPTILO- LITE, A NEW SPECIES

War-onuan T. Scnelr,Bn, U. S. Geologi'calSuraey. INrnooucrtoN The preceding description of ptilolite from Utah, confirms previ- ous determinations of its orthorhombic character and shows its formula to be lOSiOz.AlzOa'RO'7HrO. The analysesof mordenite, as given in the literature, show a very similar composition, but optical examination showsits fibers to have a small but definite inclined extinction. Grouping all the availab.leanalyses of mordenite, ptilolite, and related minerals (flokite), as far as possible, into two groups, depending on whether the material has parallel or inclined extinction, has shown that there are three distinct minerals, very similar in their properties. Conflicting statements as to their relationships have been published; thus Blggildl has urged the identity of flokite (shown to be mordenite) with ptilolite, and Walker the identity of ptilolite with mordenite. By correlating the published data as to composition, crystallography, and optical properties, supplemented by new determinations, it is shown that three distinct speciesare represented by these high-silica, acid-insoluble, zeolite-resembling minerals : 1. Mordenite (How, 1864),9SiO, . AlzOr' (Ca, K2, Na) O ' 6HrO. Monoclinic or triclinic, with inclined extinction of about 5o. 2. Ptilolite (Cross and Eakins, 1886), lOSiOz'AlzOs'(Ca, K2, Nar) O. 7HzO. Orthorhombic, with parallel extinction. 3. Clinoptilolite. The mineral from Wyoming describedby Pirs- son in 1890and acceptedby Dana (6th ed.) as crystallized mordenite. It is evidently a dimorphousform of ptilolite, lOsiolAIrOa' (Ca, K2, Na2) O'7H2O, but is monoclinic,tabular and not fibrous, with large extinction angles. It is proposed to rename this mineral from Wyoming, clinoptil'olite,referring to its inclined extinction but agreement in chemical composition with ptilolite.2 Thugutt arrived at similar conclusions,regarding ptilolite with parallel extinction as having a 10:1 silica-alumina ratio, with the formula l0siorAlros'(Ca,Naz,Kz)O.6 2/3 HzO, the formula given in Dana for mordenite. He also recognized that mordenite, with a similar formula, had inclined extinction.

1 See bibliography at end of paper for references. 2 These conclusions have been reported in The Ameri.can Mineralogi'st, vol. 8r pp' 93-94, 1923. r28 JOURNAL MINERALOGICAL SOCIETY OF AMEMCA 129

DrscussroNor ANarysns If the analyses of mordenite and of ptilolite, as given in the literature, be grouped into one of two classes,depending on whether the mineral has parallel or inclined extinction, and the ratios calculated from the analyses, it witl be found that those having inclined extinction agreewith the formula gSiOz.AlrOr.RO.6HrO (mordenite), and those with parallel extinction agree with the formula lOSiOz.AlzOa. RO . THrO (ptilolite), with the exceptionof the mineral from Wyoming, described by Pirsson, and here called clinoptilolite. Grouping all the analyses, according to their ratios, under one or the other of the two formulas given, the analyses of mordenite are as follows: Arvervsrs ol MonnnNmn

Number

Locality Tyrol Nova Nova Scotia Scotia

Walker Biblio. How ugut Ross & Shannon Parsons Parsons ref. 1 9 t6 t4 15

SiOr 68 40 66 86 67.69 67.08 67.18 64.84 65.88 67.24 66 25 Al,o, 12 77 12 13 t2.43 11.85 12.36 L2.07 12.40 12 94 11.88 CaO 3.46 3.86 2.65 1.56 3.42 3.08 3.52 2.72 2.75 NarO 2.19 24L 436 4.74 334 380 3.52 4.08 405 KgO 016 o67 2.O8 o.47 0.38 0.56 0.36 0.69 HzO 13.02 t3.87 12.84 13.23 14.79 13 40 13.44 13.85 FerOr 0.03 0.31 o24 Mgo ol7 0.09 026 0.48 0.44

Total 100 00 100 00 100 57 100.46 99.22 99 76 99.91 Extinction Snalla 7'-8. Smalla 3"40' Small

3 Determined by the writer.

The second analysis given by Walker and Parsons (Biblio. 1a) is omitted as the sample contained "small spherical radiations of some other zeolite." The ratios calculated from these analysesare given below, com- bining CaO, Na2O, and K2O into RO. In obtaining the figures, a weighted average is taken for each analysis, instead of arbitrarily taking any constituent as unity. A glance at the figures reveals not only a very close similarity for each constituent in the difierent analysesbut shows very close agreement with the formula 9SiO2. AlzOs'RO'6HrO. 130 TE E AM EMCAN M II{ ERALOGIST

Rrrros or AN.nrvsusor MoRDENTTE

Number 5 Av.

SiOr 9.06 | 9.11 9.06 8.531 8.861 8.96 8.83 8.95 x 1.0119x 1.0r 9Xl.01 x0.99

AlzOr.. 0.98 | 0.95 098 0.9410.981 1.02 0.93 0.97

RO.... 0.96| 1.03 0.98 1.0011.121 1.01 1.07 0.99

HO..... 5.98 I 5.8s 5.98 6.521 6.031 6.00 6.17 6.07 xr.ool6xo x1.0916X1.0116X1.xl. x1.01

The analyses of ptilolite, with a 10:l ratio of SiOz to AlzOg' are as follows: ANar,vsrs ol PrrLoLrrE

Number l0

Crowu Cwter Prince Faroer I Faroer lGuadal- Locality Elba lceland County, Islands I Islandslslands I canar Island

Cross Cross Biblio. and and D'Achi- Lind- ugut Schaller ref, Eakins Eakins ardi striim t 6 7 8 9

SiOa.. 67.83 70.35 67.52 65.21 67.1s 78.70 14.34 ol .zJ O/.JJ AlzOr tt.44 11.90 1o.76 IL.20 11.63 8.84 10.92 11.49 CaO 3.30 .1.6/ 3.31 3.77 2.33 L.99 2.!8 1.83 3.87 263 Nalo 2.63 o.77 1.19 a.ot 4.46 2.08 3.92 K,O o.64 2.83 1.69 I o.72 0.30 0.43 0.58 0.11 HrO 13.44 10. ':'.n'. \r+.zz 13.9E 9.71 12.05 t4.91 13.95 FeOr.. 0,09 0.29 Mgo . tr, tr. 0.34

Total...... 99.28 99.90 98.90 too.47 100.36 100.00 100.58 100.02 99.40 Extinction. 0"b 0' o'b

" Seefootnote under table showing ratios. b Determined bv the writer. JOURNAL MINERALOGICAL SOCIETY OF AMERICA I3I

The ratios calculated for these analvses are as follows:

Rarros or Awerysns or.Prrr,or,rrn

to.23 10.06 10.00 9.83 (') (') 9.78 10.04 9.98 10xt 10x1.0 10x 1.0010x0.98 10x0. 10x1 10x r.00

1.00 0.94 1.00 0.93 0.91 0.94 0.9t

RO 0.98 0.97 0.86 0.95 0.94 0.96 0.97

HzO 6.79 n s8b 7.16 7.18 6.94 7.26 6.94 7.06 7x0.' 7xr.02 7x1.03 7 X'O. 7xo. 7X1.0r o Ratios not given as sample analyzed was mixed with silica. b ,,The The ratio of the water is low. The authors state that mineral began to lose water at a very low temperature and even on drying in the air bath at 100.C. there was a noticeable loss; the amount thus lost, however, was found to be regained upon exposure to the air, and before the analysis was made the material was allowed to remain loosely covered for several days.,'The sample was analyzed,in the ,,very dry" climate of Denver. The authors suggest that the Denver climate ,,may hav€ had suficient desiccating power to remove part of the water from the mfureral analyzed there."

The ratios are in very closeagreement with the formula 1OSiOr. AlzOa'(Ca, Na2, Kr)O' 7HsO. The distribution of the CaO, NazO, K2O, and MgO, as given in the analyses,which have been grouped together as RO, on the basis of ratio percentages,is as follows, given with decreasingCaO. The table shows that there is no distinction in the distribution of the RO basesbetween mordenite and ptilolite. CaO is 50 per cent or over in 3 mordenites and 4 ptilolites; NazO is 50 per cent or over in 4 mordenites and 2 ptilolites. In both of these minerals, CaO and NazO seem to be mutually replaceableto almost any extent. fn no analysis,is KzO over 33$per cent. In the singleanalysis of clinoptilolite, the CaO, NarO, and KzO are present in the ratio of 1:1:1. 132 TEE AMEKICAN MINERALOGIST

PencBNrlor ol BlsBs Gnoupno .ts RO, wrrn DncnnasrNc CaO

Analysis No. Mordenite Ptiloiite NazO Mso

11 P 62 rr 27 l2 P 62 20 18 I M 623530 18 P 6t 38 1 .. 2 M 583363 l0 55 39 6 .. 51 45 4 .. 15 P 49 47 4 .. 7 M 464149 6 M &4835 t6 P M 51 5 .. M 40 58 .. 2 8 M 395236 9 M 375058 t4 P 35 59 6 -. "19 3132334 t7 P 305857 A M 22 60 18

" Clinoptilolite from Wyoming.

Cr-rNoprnor-rrB The clinoptilolite fromWyoming, described as mordenite, is entirely different in habit, forming thin tabular crystals, like those of heulandite. Pirsson's analysis agreesclosely with the formula for ptilolite,the ratiosof SiOz:AlzO3:(Ca,Nar,Kz)O:HzObeing 10.10: 1.04:1.05:6.78.The refractive indices,determined on part of the original material, kindly supplied by ProfessorW. E. Ford from the Brush collection, are given below. Oprrcar- PnopBnrrns The determinations of the optical properties of mordenite, and ptilolite, as given in the literature, may be brought together in the following two tables, extending the data given by Ross and Shan- non. JOURNAL MINERALOGICAL SOCIETY OF AMERICA 133

Oprrcel Pnopnnrms or MonorNrm

Locality Sign Extinction

Idaho r.475 1.477 r.478

Idaho (1) r.470 t.475 l.+/J X 1\c:3"40t, Z:b Idaho (2) r.472 t.475 1.476 Small Idaho (3) 1.473 Idaho (4) , r.t/J Nova Scotia (How) .. r.473 Small Nova Scotia (Walker r.471 1.475 Small and Parsons) Iceland 1.472 r.474 5"

Average 1.472 r.474 r.476 About 5"

Olrrcer Pnopontms oF Prrr,or,rrE

Locality Sign Extinction

Colorado 1.476 1.480 1.480 0' Utah r.473 1.475 r.478 00 Elba 1.480 1.482 0' Iceland 1.480 0'

Average r.474 1.478 1.480 00

Clinoptilolite is optically negative. Z to a-axisis 15", whence I to c-axis:16]o, accordingto Pirsson.Crushed fragments show extinction angles of about 34". Larsen determined a as 1.476 and. 7 as t.479;2 V vety small,dispersion p( u strong. Cleavageb(010), nearly I I/.

BIBLIOGRAPHY 1. How, D. C. L., On mordenite, a new mineral from the trap of Nova Scotia: Jour. Chem.Sac. (London), vol. l7 (newser. vol. 2), p. 100,1864. 2. Cross,W., and Eakins,L. G., Communi.U. S. Geol.Suraey, Div. RockyMoun- tains, YIII. On ptilolite, a new mineral: Am. Jour. Sc., 3d ser., vol. 32, p. lll, 1886. 3. Pirsson,L. V., On mordenite:Am. Jour. Sc.,3d ser.,vol. 40,p. 232,1890. 4. Cross,W., ahd Eakins, L. G., A new occurrenceof ptilolite: Am. Jour. Sc., 3d ser.,vol. ,t[4,p.96,1892. 5. Clarkd, F. W., Note on the constitution of ptilolite and mordenite:Am. f oru. Sc.,3d Ser.,vol. r[4,p. 101,1892. 134 THE AMERICAN MI N ERALOGIST

6. Colomba, L., A new variety of ptilolite from Crownprince Rudolph Island: Alli d. R. Acca.d.Sci. Torino,vol.37'p. 553,1902. 7. D'Achiardi, G., Zeolitesfrom the veins of Speranzanear San Piero in Campo, EIba:At'ti il. Soc.Toscana d. Sci.Not., vol.22,p.150' 1906. 8. Lindstrdm, G., Investigation of ptilolite from Teigarhorn,Iceland: Geol.Fiiren. Fdrh.,vol.29, p. 106,1907. 9. Thugutt, St. J., Mordenite from Tyrol and the Faroer: Com'pl'renil. Soc.Scien- Vorsoai'e,vol. 5, p. 76,1912.Abslu. Neues f ahrb.Min', GeoI.,Pal.,l9l3(2),p. 33. 10. Callisen, K., Flokite, a new zeolite from lceland: Meddel'.Dansk. Geol.Fdr., vol 5, No. 9,l9l7 . 11. Koch,L. H., A newoccurrence of ptiJolite:Am. Mineral.,vol. 2, p. 143,1917. 12. Tschermak, G., The chemical composition and behaviour of the zeolites: Sitz.K. Acail.tl. Wissensch.Wien, vol.126' Abt. I, (pp. 541-606),p. 547, 1917. 13. Blggild, O. 8., Re-examinationof some zeolites: Det. Kgl. Donske Vidensk. Selsk.,Malh.-Jys. Meililel, vol.4' (8),p. 19,1922. 14. Walker, T. L., and Parsons,A. L., The zeolitesof Nova Scotia: Conlribulionslo ConadianMi,neral,ogy,1922: Unitersity ToronloStud,ies, Geol. Series No. 14, p' 59,1922. 15. Walker, T. L., and Parsons,A. L., Tn-eNorth Mountain basalt of Nova Scotia: Glaciation,Tubular amygdaloid,mordenite, and louisite: Conlri'butionslo Cona- d,ianMineral,ogy,L923: (Inhersity TorontoStuili'es, Geotr. Ser. No. 16, p. 10, L923' 16. Ross,C. S., and Shannon,E. V., Mordenite and associatedminerals from near Challis, Custer County, Idaho; Proceeil.Uni,led States Nati'onol Museun,, vol. 64,pp. l-19,1924. 17. Schaller,W. T., Ptilolite from Utah: precedingpaper.