MINERAINACAL NOTES 30s Tart, A. S. (1955) J. Gemology 5,65

MINERAINACAL30sNOTESLanc, S. M., C. L. Frr,uonr erqoL. H. Mexwul (1952)J. Ras,U. S.Nat. Bur. Sl'anil.48,298-3t2.Tart, A. S. (1955)J. Gemology5,65-72.Wnrsrnn, R. (1962)Gems,YoI.1,Butterworttrs,Washington,D. C., p. 307.Wrxrmn, E. R., J. F. SnnvnneNoI. B. Curr,nn,/. Amer. Ceram.Soc.49r63 -637.Yauecucut, G. (1944)f . Jopan Cerum.Assn.52, G7 ,THE AMERICANMINERALOGIST,VOL. 53, JANUARY.FEBRUARY,1968THE INFRARED SPECTRUMOF DAWSONITEParnrcre A. Esrap ANDCLARENcEKARR, Jx., Morgantown Cool ResearchCenter, Bureau of Mines, U.S. Departntent of the Inter'i,or,Morgantoun,West Vi,rginia.h.rrnonucrtoNAs part of a broad program on minerals researchby the U.S. Bureauof Mines, infrared spectroscopyis being used at its Morgantown, W. Va.,laboratories for the study of various minerals of current interest to bothGovernment and industry. One of these is the mineral dawsonite, abasic carbonate of sodium and aluminum, NaAl(COa)(OH)r. e recentreport (Smith and Milton, 1966) describesrelatively abundant depositsof this mineral as a rock-forming constituent of oil shale in the PiceanceCreek Basin of northwestern Colorado. This occurrence has created interest in dawsonite as a potential ore of aluminum. In addition, alkalizedalumina (synthetic dawsonite) prepared by the reaction of aluminumsulfate and sodium carbonate, is being tested by the Bureau of Minesas an absorbent for sulfur dioxide in flue gas. This note presents the infrared spectrum of pure natural dawsonite, compares it qualitativelywith synthetic dawsonite, and demonstrates that infrared spectroscopyto 200 cm-1 is a reliable method for the identification and possiblequantitative analysis of this mineral.ExpnnruBNrar.Dawsonite is a colorless to white transparent mineral and occurs asrosettes of bladed to acicular crystals (0.05-0.5 mm) (Stevenson andStevenson,1965), as thin incrustations, or as sedimentary nodular accretions. A few milligrams of pure dawsonite were isolated microscopically(40-100X) from each of the three sourcesshown in Table 1. The relativehardnessof 3 for dawsonite greatly facilitated its isolation from the matrix minerals. About 0.5 mg of the isolated samplewas weighed on a microbalance, ground for 5 minutes with 500 mg of cesium iodide in an agate

306MINER-ALOGICAL NOTESball mill and this mixture pressedinto a 0.8X 13 mm pellet. The infraredspectrum was then scanned on a Perkin-Elmer 621 infrared gratingspectrophotometerpurged with dry air. This instrument extends therange of the mid-infrared from 650 to 200 cm-l, adding severalusefulabsorption bands to the infrared spectrum of many minerals (Karr, etal., 1967). The associatedminerals and matrices listed in Table 1 werealso identified by their infrared spectra and the dawsonite spectrum foreach specimencheckedfor possiblecontamination from these minerals.The spectra were also examined for evidenceof other known accessoryminerals peculiar to the various localities (Hay, 1963; Palache, et al.,1951; Smith and Milton, 1966; Stevensonand Stevenson,1965).TanmLocalityMcGiIl University,Montreal, Canada1. DalvsoNnrSawr,a DnscnrprroNsDescription and associatedmaterialsSourceMrs. Louise S. Stevenson, Redpath Museum, Montreal CanadaBladed crystals and rosettescoating the joint plane of a feldspathic dike. Specimensize: 3')(\'1lt,Komana, northernAlbaniaWard's Natural Science Establishment, Inc , Rochester, N. Y.Rosettes of acicular crystals associated with realgar on host ofsilica. Specimensize: l"\l "OlduvaiTanzaniaDr. Charles Milton,GeorgeWashington University, Washington, D. C.Sedimentarynodular accretions(up to 7/4"), encrusted withclayGorge,The purities of the three dawsonite specimenswere further substantiated by X-ray diffraction. Spacingson the patterns agreedwell with theASTM Powder Diffraction File, Card 12-449,exceptfor someline intensitv differences.Rpsums ANDDrscussroNInfrared spectra for dawsonite from the three localities are shown inFigure 1 and the absorption bands listed in Table 2. The agreement,inboth frequenciesand relative intensities, supports the authenticity ofthe infrared data. The two strong bands at 3280 cm-l and 1555 cm-1can be assignedto O-H stretching and bending vibrations, respectively.The position of the O-H stretch indicates that hydrogen bonding contributes to the cohesiveforcesof the crystal lattice. The strong band at1390 cm-l can be assignedto the asymmetric stretching vibrations

MINERAINGICAL NOTESW A V E L E N G TmHi,c r o n s728910t!z.F azF1,800 1,600 1,400 1,200 1,000800-1F R E Q U E N CcYm,600400( a ) M o n t r e a lC, anada(b)N.Albania( c ) E . A fr i c a(d) SyntheticFrc. 1. Infrared spectra of natural and synthetic Dawsonite'

308MINERAI,OGICAL NOTES(z) of the COe radical. ft occurs at a frequency somewhat lowerthan the range for a large number of normal inorganic carbonates (1450to 1410cm-l) (Bellamy, 1958) and carbonateminerals (Adler and Kerr,1e63).The identification and quantitative estimation of dawsonite by theinfrared method in the presenceof commonly occurring accessoryminerals is highly favorable as was shown by a study of the infrared spectraof a number of theseminerals.The two strongestbands of dawsoniteat1390 cm-l and 1555 cm-l occur in a region not seriously overlapped bythe principal bands of sulfates (1130 to 1080 cm-r), silicates (1100 to900 cm-l), phosphates(1100 to 1000cm-l), nitrates (1380 to 1350cm-r)(Bellamy, 1958), and clays (1100 to 1000 cm-l). Sulfides and oxidesgenerally have absorption bands at lower frequencies.We examined theTenrr 2. INrunro AtsonptroNB.q,uosor.Ne,runalDewsoxrrrFrequency, cm-l (relative intensity) I24s (w)274 (w)297 (m)3s4 (w)385 (w)482 (m)s03 (m)I s:strong, m:medium,539 (m)685 (m)723 (w)840 (m)8s6 (w)928 (m)948 s(s)3280(s)34s0(w)weak,infrared spectra of samplesof dawsonite-bearingoil shalesfrom colorado.These spectrashowedstrong bands for dawsonite,dolomite, microcline,and quartz, and weak organic bands. The presenceof the organic mattermade it extremely difficult to isolate pure dawsonite microscopicallyfrom this source.The development of a successfulquantitative procedurefor the estimation of dawsonite in these and other mixtures, however,is contingent on obtaining enough pure mineral as a standard so thatstudies can be conducted on particle size reduction versus absorptivity.From band intensity measurements on the isolated pure mineral, weestimate that amounts as small as 1 to 3 weight-percentcan be detectedin mixtures, compared to a recently published estimation of X-ray detectability at 3 percent (Smith and Milton, 1966).Synthetic dawsonite,prepared by W. R. Grace and Co., Baltimore,Md., was examined and its spectrum (curve d, Figure 1) showed goodagreementwith that of natural dawsonite.The X-ray data for this samplealso agreed well with that of natural dawsonite. rrowever, the lines for

309MINERAI.OGICAL NOTESthe synthetic material were more diffuse and no back reflection lines wererecorded, indicating a difierence in the degree of crystallinity of the twomaterials.AcrNowleocunr.ttWe wish to thank John J. Renton, Geology Department, West Virginia University, forobtaining the X-ray data;L. G. Berry, Queen's University, Kingston, Ontario, Canada,for providing further X-ray data on dawsonitel and John Ward Smith, Laramie PetroleumResearch Center, Bureau of Mines, Laramie, Wyoming, for supplying samples of dawsonite-bearing oil shales.Rrrnn-nNcnsAor,nn, H. H. eNo P. F. Knnn (1963) Infrared spectra, symmetry and structure relationsof some carbonate minerals. Amer. Minual'.48, 839-853.Bnrr.anrv, L. J. (1958) The InJrareil Spectra oJ Compler Mol'ecules.John Wiley & Sons, Inc.,New York.Hrv, R. L. (1963) Zeolitic weathering in Olduvai Gorge, Tanganyika. Geol'. Soc. Amer.Bull.74, 128l-1286.Kann, C., Jn., P. A. Esrnp, eNo J. J. Kovacn (1967) Infrared analysis of minerals in coalusing the 650 to 200 cm l region. Chem.Inil. (London),9' 35G357.eno C. Fnolrlnr- (1951) The System of Mi.neroJogy of JamesPALAcEE, C., H. Brnulx,Dwight Dana anil Etlward' Salisbury Dano, v. 2. John Wiley & Sons, Inc., New York.Surrn, J. W. .qrl C. Mrr.tolt (1966) Dawsonite in the Green River formation of Colorado.Econ. Geotr.61, 1029-10 2.Srn',onsoN, J. S. axo L. S. SrnvrNsor (1965) The petrology of dawsonite at the type locality, Montreal. Can. M i,neraJ.8, P att 2, 2 9-252.THE AMERICANMINERALOGIST,VOL. 53, HETtil"frTR:ETrHlruMPaur- B. Moone, The Department of GeophysicalSciences,Unit:ersity ofChicago,Chicago,Illinois.INrnolucrroNA systematic study on the crystal chemistry of manganesesilicatesprompted further investigationson gageiteand harstigite, two rare andpoorly understoodspecies.These studiesindicate that the two mineralsare structurally related but their unusual compositions are difficult tointerpret without recourseto crystal structure analysis.GecBrrBGageite was frequently found during mining at Franklin, SussexCounty, New Jersey, its only reported locality, though it could hardly

ball mill and this mixture pressed into a 0.8X 13 mm pellet. The infrared spectrum was then scanned on a Perkin-Elmer 621 infrared grating spectrophotometer purged with dry air. This instrument extends the range of the mid-infrared from 650 to 200 cm-l, adding several useful absorption bands to the infrared spectrum of many minerals (Karr, et .