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MINERALOGICAL NOTES
1305
ammoniumbicarbonate,was depositedinside the
Teschemacherite,
wellheadof the Broadlandsgeothermaldrillhole BR 9 after the bore
had beenshut for severalweeks.
The crystals,white and up to 4 mm long, were identified by X-ray
The deposit,which filled the 198
diffractionand infra-red spectroscopy.
mm diameterpipe to an estimateddepth of about 0.5 m, was ejected
in a block, "like a champagnecork," when the bore was opened.Gas
pressureat the wellhead prior to dischargewas 51.0 bars, the temperaturewas ambient,and the water level in the bore was about 490m
belowgroundsurface.
apparently formed from reactionbetweenCO2
The teschemacherite
and.NH3, which collect at the wellheadafter separatingfrom deeper
watrers,as represented
by: NH, * CO, * HrO ? NH+HCO:;.The gas
content of water dischargedwhen BR 9 was openedhas been calculated as 0.22molepercentof which 93.5mole percentwas COz (Browne
and Ellis, 1970) and the total NH3 content of the dischargedwaters
was 5.5 ppm (Mahon and Finlayson,1972).
has not beenreportedfrom other geothermalfields
Teschemacherite
but occursin someguanodeposits(Palacheet aL, l95l). Coresfrom
drillhole BR 9 were examinedfor the ammonium feldspar,buddingtonite (Erd et al.,1964)but nonewas detected.
RsrnRENcns
BnowNr, P. R. L., euo A. J' Er,r,rs(L97o)Amer. J.$ci.269,97.
Eno, Rrcnann C., DoNer,o E. Wrfltn, Josnpn J. Fennr, awl Dower,n E. LnP (1964)
Amar. Minerar. 49, 831.
M,rnow, W. A. J., ewo J B. Frxr,evsox (1972)Amer. J.9ci.272,48'
Per,ecrro, Cnenr,ns, Hennt BnnueN, AND Clrrronn Fnorvlnr, (196D Svstem o!
Minnralogy ol , . . Dnna, u.2,Tth ed. JoinnWiley and Sons,Inc., New York,
Ll2L p.
American Mineralogist
Vol.57, pp. 1305-1309 (7972)
A SIMPLE HEATING STAGE FOR SINGLE-CRYSTAL
DIFFRACTION STUDIES UP TO IOOO"C
Josnpu R. Smvtu, Department of Geologiaal Sci,ences,
H aru ar d U ruiuersity, C ambrid,g,e,M ass.02 138
AssrBacr
An inexpensiveheating stage for single-crystalX-ray diffraction studies up
to 1000"has beendeveloped.The furnaceis capableof maintainingtemperatures
from 20' to 1000"Cto within :L 10"C indefinitelv.
1306
MINEilALOGICAL NOTES
Dpscnrprror.r
Much information about'the crystal chemistry of silicates can be
obtained by refinement of the crystal structures from high_tempera_
ture single-crystal diffraction data. The developmentoi automated
single-crystaldiffractometersand high speeddata processingequip_
ment now allows such refinementsto be rapid, routine, and precise.
A
simple heater has been designedfor use with a picker four-circle
goniostat.This devieecan easily be reproducedfrom
the plans given
in Figure 1 for a fraction of the cost of any commerciaily-available
neater.
several high temperaturestagesfor various single-crystar diffraction
geometrieshave been descirbedin the literature.
Reviews of those
developedbefore rg64 are presentedby Gordschmidt (1964)
and
Buerger (1964).More recenily,Foit and peacor (196z)
have described
a furnacefor'weissenberggeometry,and viswamitra and
Jayalakshmi
(1970)have describeda heaterfor a Hilger and
watts diffractomerer.
wilh-in the last year' a small furnac" .uitubr. for use with precession
and,four-circle geometrieshas becomecommercialy availabie
through
Blake rndustries.The latter two devicesheat crystar. pri-urity
ry
radiative transfer, which may cause uncertainties in
temperature
measurementif the crystar and thermocouplehave different
thermar
absorptionproperties.rn addition, if the crystal or its X-ray
transpareltl capsuleis exposeddirectry to incandescent
platinum, there is a
possibility of evaporatingan opaqueplatinum film
onto the crystal.
Another furnace capabreof mainlaining crystal temperatures
to
-t0.loc has beendescribedby Lynch and Moros-in(lgzr).
This device,
however,is rather expensiveto buird becauseit requires machining
small hemispheres
of beryllium. rf, however,a temperatureprecisionof
:t10oc can be tolerated a much ressexpensiuu
iu*u." can be constructed.
To measurediffractedX-ray intensitiesfrom a crystal at high temperatures,an extremelylocarizedheat sourcemust be emproyel
which
is stableover a period of severardays and has a geometrywhich
does
not block the incident or diffractedX-ray beams.An instrument
has
been designedand constructedto meet theserequirements.Mounting
techniqueswhich allow temperaturemeasurementto within I0"c,
d;
not obstruct the x-ray beams,and prevent oxid.ationof ferrous iron
have beendevelopedfor usewith this instrument.A dimensionedshop
drawing of the device as adapted for use with a picker four-circle
goniostat is given in tr'igure 1. A diagram of the high temperature
goniometerhead appearsin Figure 2. The device mounts in
tire p
MINERAI,OGICAL NOTES
1307
D CuTubiry
Frc. l. A longitudinal section through the heater. All dimensions are in inches.
A small twist of Pt foil is placed in the cool end of the pyrophyllite tube to
cause turbulent flow of nitrogen through the furnace and eliminate temperature
gradients across the orifice. The thin wall of the pyrophyllite tube is threaded
at 44 turns per inch to separate the windings of 0.015 inch diameter Pt wire. A
current of 6.0 amperes at x) volts AC was required to maintain the crystal at
900'C at a distance of 3 mm from the orifice.
rotation circleoppositethe goniometerheadand parallel to the 4-rotation axis. with modificationof the baseof the brasstube, the heater
and high temperaturegoniometerhead are also suitable for use with
cameras.
precessionand \Meissenberg
The device illustrated consistsof a telescopingbrass tube with a
small platinum-wound, fired pyrophyllite furnace in one end. The
furnaceis positionedso that the crystal is three to eight mm beyond
the opening.A small flow of nitrogenis maintainedthroughthe furnace
to transfer heat to the crystal. The furnace end of the brass tube is
water-cooledusing a coil of t/g inch O.D. coppertubing. Temperature
fluctuationdueto air currentsin the room arepreventedby a cylindrical
screenof 0.003inch thick Dupont Kaptonl high-temperatureplastie
film.
The 0.020inch wall thicknessof the threadedpyrophyllite tube is
Relatively low flows of nitrogenthrough the furnace (oneto two liters
per minute) areused.
As shownin Figure 2, the crystal is mountedin an evacuatedsilica
glasscapillary, and held in place by me&nsof silica glassrods sealed
l Registered trade ma,rk of E. I. Dupont de Nemours Co'
1308
MINERALOGICAL NOTES
Pt Foil Disk
Mullite
T.C.Tubing
0.002Pr-Rh
Thermocouple
Crystol
Silict Copillory
,
lcm
,
Supper Z-tronslotion
Goniometer Heod
Frc. 2. A section through the top of a Z-translation goniometer head (Charles
Supper Co.) modified for high temperature studies. The standard Z-translation
block has been replaced by one made of Bakelite plastic open at the rear for
e.mergenceof the thermocouple wires. very fine thennocouple wire must be used
to prevent heat conduction down the wire. Alumina cement is used to
attach the silica capillary to the 0.075 inch diameter thermocouple tubing.
in eachend of the capillary. This type of mount was found to produce
negligiblescatteringand absorptionof X-rays and to be stableat temperaturesas high as 1150oC.Oxidationof ferrousiron can be prevented
by flushingout the capillary with hydrogenbefore'evacuation
and sealing. The temperatureis measuredusing a 0.002inch diameterpt-ptl0
percentRh thermocoupleplacedaroundthe outsideof the capillary. A
0.75inch diameterplatinum foil disk is useda,sshownto preventexcessive heatingof the goniometerhead.This devicehas beenusedsuccessfully for routine automatic measurementof X-ray intensity data from
ferrous-ironpyroxenemineralsat temperaturesas high as 1000'C.
AcrNownncrltpwr
The author wishes to thank Profes,sorCharles W. Burnham for help in preparing the manuscript and the National science Foundation for Grant No. GA-12g52.
Rnrnnnucns
Bwncnn, N. J. (196l[) The Precession Meth,od,. John Wiley & Sons, fnc., New
York, p. 247-2ffi.
Forr, F. F., eNo D. R. Poacon (1967) A high temperature furnace for a single
crystal X-ray diffractometer. J. Sci..Instr.44, 183-185.
Gomscrrnrnr,
. J. (1964) BiblingraphE I: HiAh temperature X-rag difraction
techniquc,s.International Union of Crystallography, Commission on Crystallographic Apparatus, Utrecht.
MINERALOGICAL NOTES
1309
LrNcu, R. W., eNr B. MonosrN (19?1) A novel furnace for high temperature
single crystal X-ray diffraction studies. (abstr.) Amer. Crystallogr. Assoc.,
Winter Meet, Progr., p.58.
vrswanrrna, M. A., aNo K. Jeyer,ersnvr (1970) A simple miniature furnace
for routine collection of single crystal X-ray data up to 1000'C on the Hilger
and Watts linear diffractometer. ,I. Phgs. E : Sci,.In"str. 3,65ffi57 '
American Mineralogist
Vol. 57, pp. r309-r3r0 (1972)
ANTIPHASE DOMAIN STRUCTUREOF TIIE
INTERMEDIATE COMPOSITTONPLAGIOCLASE
FELDSPARS:ADDENDUM
es
atseienn
e
c G C'NN
;;:#:#hsic
T,";;?:"?,T:T
AND
S. W. Berr,pv,Departmentof GeologEan'dGeophgsics
Uni'uer si,tyof Wisconsin,M ad:ison
We wish to thank Dr. M. G. Bown and Dr. P. Gay for pointing out
to us that certain statementsin our recent article (cinnamon and
Bailey, 1971)are opento misinterpretation.The statementsof concern
of
1/lSl hasbeencitedas a measure
are (p. 1f85) ... "Thereeiprocal
domainsizeby smith and Ribbe (1969).This usageof equation(2) is
basedon the assumptionthat the samesplit-"b" reflectionsare being
viewedin projectionsalong lhe r, y, and a axes,howevet,and reduces
system'
to a one-dimensional
the antiphasestructureof the plagioclases
This is an unprovenassumptionthat has becomeacceptedas a basic
,,truth" in the literature concerningthe structure of the intermediate
It seemsmuch more probablefrom the gencompositionplagioclases.
eral nature of the results discussedbelow that entirely different reflectionswith different splitting vectors are being viewed along each
axis.tt . . .
The original intent of thesestatementswas to questionthe interpretation of the intermediateplagioclasedomain systemas a one-dimen-