American Mineralogist, Volume61, pages100-107, 1976
The deepblue Maxixe-type color centerin beryl
Kunr N.{ssAU,BETryE. Pnnscorr, ANDD. L. Wooo
Bell Laboratories,Murray Hill, New Jersey 07974
Abstract
A deep-bluecolor center can be introduced into some beryl by gamma ray, X-ray, or
neutron irradiation. If the original color is yellow or green,then a green or blue-greencolor
can result from introduction of the samecolor center.This color centeris characterizedby: ( I )
strong dichroism with the intenseoptical absorption in the ordinary ray;(2) narrow band absorptions in the 5000 to 7000 A region in the ordinary ray only; and (3 ) fading of this center on
exposureto light or on heatingto above 100"C. Very similar material, showing an absorption
spectrumdiffering only in minor details,was found in Brazil at the Maxixe Mine about 1917,
and the modern material has been named "Maxixe-type" beryl.
Introduction
of Commerce, who kindly permitted us to use part
for experimentatiop.
In l9l7 a deep blue ("indigo," "cobalt," or
A total of 235 specimensof pale-coloredberyl were
"sapphire"-blue) beryl with properties quite distinct also tested for their susceptibilityto gamma rays in
from those of aquamarine was found in the Maxixe developing this color center. These specimens inmine in a 4-5 m deep pit some 50 m from the Piauhy cluded a number of those used in previous studies
River, southeastof Arassuahy,in northeasternMinas (Wood and Nassau, 1967, 1968) as well as others
Gerais, Brazil. When it was discoveredthat the color from a variety of locations, mostly in Brazil.
faded on exposureto light, the mine was abandoned
In Table I are listed the original 1917 Maxixe
and the location has becomelost. A brief report was specimen,the 31 specimenswhich showeda deepblue
given by Wild in 1932and more details,including ex- or green Maxixe-type spectrum as we received them,
tensive refractive index data, were published by and eight additional beryl specimensin which we
Schlossmacher and Klang and by Roebling and
were able to develop deeply colored Maxixe-type
Tromnau, both in 1935.
spectra. A further 25 beryl specimens showed
When deep blue beryl (Crowningshield, 1972-73) noticeable,but only weak, spectraof this type after
having similar but not identical characteristicsap- irradiation and are not listed; the remaining 170
peared recentlyin the jewelry trade, a detailedstudy specimensshowed no noticeablechange.
of this material was undertaken. Deep green and
Sampleswere cut and polished with the hexagonal
blue-greenforms also becameavailable,and color il- axis in the plane of the specimen.Polarizedabsorplustrationshave been published (Nassau, 1973;Nas- tion spectra were recorded on a Cary Model 14
sau and Wood, 1973), the latter showing the better spectrophotometerin the range from the absorption
color reproduction of the two.
edge near 2000 A out to 25,000A. Absorption data
for faceted gemstoneswere taken with the stones imExperimental
mersed in carbon tetrachloride in a fused silica cell to
Samples of current deep blue and deep green reduce refraction at the facets. Samples were kept in
material were obtained by courtesyof Mr. R. Crown- the dark when not being examined,and the brief light
ingshield of the Gemological Institute of New exposurein the dispersedradiation during absorption
York City, Mr. H. Rubin of the GemsetCompany of
measurementswas insufficient to cause significant
New York City, and Dr. E. Giibelin of Lucerne, bleaching.
Switzerland.A fragment of the 1917 Maxixe Beryl,
Irradiations were carried out with gamma rays in a
which had been kept in the dark sincethat time, had Cobalt-60 cell at 0.70 megaradsper hour. Neutron irbeen given by Mr. F. Quast of Idar-Oberstein to
radiation was carried out in the Brookhaven reactor
G . O . W i l d ( W i l d , 1 9 3 3 )a n d t h e n c e t o M r . B . W .
at 1013fast neutrons plus l0P slow neutrons per cm2
Anderson of the Laboratory of the London Chamber per second. X-ray irradiation was effected with a
100
l0l
DEEP-BLTJEMAXIXE-TYPE COLOR CENTER IN BERYL
TlsI-e l.
M a x i x e a n d M a x i x e - T y p e S p e c i m e n sU s e d i n T h i s S t u d y
Specimens
and Maxixe-TyPe
Used in This Study
Maxixe
A.
592
s93
594
6Il to 5I3
618 to 638
639 to 54I
B.
446***
A A1***
480***
506***
596
597
598
599
Maxixe
G-MT
G-MT
B-M
B-MT-Gem
B-MT-GEn
B-MT
B-MT-GemS
B-MT-GemS
G-MT-Gems
589
590
59l-
Color
When Bleached
Origin*
Type*
Desiqnation
or
Maxixe-Type
^^l
^rl
acc
pale pink
pink
pale pink
pa.le pink**
pale pink**
yellow* *
Golden or Color1ess
Aquamarine,
Morganite,
Precursor
with Maxixe-Type
B-MT
G-MT
G-MT
B-MT
BG-MT
BG-MT
BG-MT
B-MT
Medium
Medium
firgn
Medium
Medium
High
Medium to High
Beryl
colorless
Yell-ow
pale aqua green
pale aqua blue
pale yeLlow
yellow
deeP Yel1ow
Pink
Brazil
Braz iI
North Carolina
Unknown
BT?
Br?
Br?
Br?
Content
as Received
yeIlow**
pale yel-Io$t
Br?
Br?
Braz]-I
L9I7
BT?
BT?
BT?
BT?
BT?
BT?
Alkali
Lo$,
Low
High
Medium
Low
Low
Low
Hrgn
19I7 Maxixe, MT-Maxixe-Type; GemB-BIue, G-Green; M-original
f a c e t e d g e m s t o n e ( 5 t o I c a r a t s i n s i . z e ) , a l l o t h e r s p e c i m e n s are
or said
from BraziI
Br? probably
or fragments of crystalst
crystals
to be from Brazil.
Not bleached; color
ordinary ray color.
deduced indirectly
from examination of the extra-
P r e v i o u s l y s t u d i e d b y W o o da n d N a s s a u ( 1 9 6 7 , 1 9 6 8 ) ; n o t e t h a t
# 4 4 7 ' w a se r r o n e o u s l y l i s t e d a s # 4 7 7 i n T a b l e 1 , S e c t i o n 2 e o f
W o o da n d N a s s a u ( 1 9 6 8 ) .
tungstentarget tube operatedat 25 kV and 35 mA at
a distanceof 3 cm.
For the heat-fading experiments,small slabs (3.2
mm X 5 mm X l0 mm) of specimen ff446 were introduced into an air oven at various temperaturesin
contact with a previously equilibrated brass block
with a thin layer of siliconelubricant for good thermal conduction. The heating was continued for
various periods of time. Light bleachingwas achieved
either by placing the sample 15 cm from a standard
100 watt tungsten filament lamp bulb, or by taping
the specimen to a south-facing glass window in
daylight. We were careful to avoid heating the samples to more than 50'C during the light bleachingexperiments.
Induced radioactivity was measuredby gamma-ray
spectrometerusing a Li drifted Ge detector and a
1024 channel analyzer.
Comparison of Maxixe-tyPe beryl
with aquamarine
Polarizedabsorption spectrain the 2000 to 8000A
region are shown in Figure I for blue and green
aquamarineberyl, for the 1917Maxixe specimen,and
for current blue and green Maxixe-type material as
received for study. We designatethe characteristic
narrow band spectrum at 5000 to 7000 A as
"Maxixe" for the original 19l7 beryl from the Maxixe mine, but "Maxixe-type" for the closely related
but slightly different spectrum seenin specimens1590
and 592. The difference between the blue and green
specimens of both aquamarines and Maxixe-type
beryls lies in the position of the Fe3+absorption edge
(Wood and Nassau, 1968), being above 4000 A in
greenspecimensbut below 4000 A in blue specimens'
Chemical analvsesshow that the iron content in the
102
NASSAU, PRESCOTT,AND WOOD
green Maxixe-type specimensis very much higher
I
than in the blue material. Table2 shows very clearly
I
GREEN
I
this difference in iron content between the green
Fe3*
AQUAMARINE
I
ROUGH
specimens589 and 590 and the blue specimens591
\
#480
and 594. The characteristicline absorption between
\
e -.
Fe2+
5000A and 8000A, however,is the samein both blue
and green Maxixe-type material. Blue maxixe and
Maxixe-type specimensshowed very low concentrations of transition metals,particularly iron (0.01 perBLUE
cent or less Fe-Table 2); iron had been reported to
tt\--€tt'
AQUAMARINE
-^2+
ROUGH
be absentby Wild (1933)and at rhe 0.03 percentlevel
@
#506
by Roebling and Tromnau (1935). They did not
detectany cobalt and neither did the presentanalysis,
thus eliminating Wild's suggestionthat this might aFe3+
cause the blue color. It may be concluded that the aF
z
narrow band absorption featuresin the 5000 to 7000 Uo
M A X I X E- T Y P E
A region cannot be attributed to iron or any other I
G R E E NB E R Y L
F(OUGH
transition element.
F
# 590A
0
There are some differencesin the narrow band abcoloR
\
sorption features between the l9l7 Maxixe specimen ;
\ € CENTER
z
and the Maxixe-type specimensof current material. (I)
The differencesare more distinct when specimensare
a
cooled to near liquid helium temperaturebecausethe (D
MAXIXE-TYPE
line widths are significantly reduced (Fig. 2). The
BERYL
BLUE
location of band maxima for both room temperature
CUT STONE
*592
and l0oK are given to the nearest 5 A in Figure 2.
The room temperature absorption wavelengths in
Maxixe beryl are consistentwith those observedby
O R I G I N AIL9 I 7
Wild as quoted by Anderson (1956). These absorpMAXIXE
BERYL
tions occur only in the ordinary-ray spectrumin both
COLOR
ROUGH
Maxixe and Maxixe-type samples,and their presence
#591
---1
CENTER
provides the most reliable test for distinguishing
Maxixe-type material from aquamarine.
2000
4000
6000
8000
Another test is basedon the opposite dichroism of
I ANGSTROMS
the two materials. The blue color of aquamarine is
Ftc. 1. Spectra of Maxixe-type beryls and aquamarines;o is the
usuallycarried by the extraordinary ray, while that of
ordinary ray spectrum, e the extraordinary ray spectrum. AbsorMaxixe-type beryl is carried by the ordinary ray. It is bance : log,o(Io/l).
Tl.nte 2.
Sample
Green
Maxixe-Type
a)
Major
s90
589
*
Type
(>18)
0 .x s
O .O X B
0.00xa
0.00Oxt
Green
Maxixe-Type
Semi-Quantitative
Si,AI,Be,Mg
Fe,Li
M9,Na
Ag,K,Mn,Sc,Zn
0.I7C
594
Blue
Maxrxe-Type
Spectrochemical
Si,Al,Be,Mg
Fe,Li,Sc
Mg,Na,Mn, Zn
Ag,K,Cu
Ca, Cs
b)
Fe
Chemical Analyses
Quantitative
0.252
591
Original 1917
Maxa xe
Analysis
Si,A1,Be,Mg
Sr,Cs,Na
Mn,Ag,K,Li,Fe
Mg,Rb
Ca, Cu, pb,Ba
Si, AI, Be,Mg
Sr,Cs,Na
K,LA
Fe, Rb
Ca. Cu, M9, Pb,Ag, Ba
Analysis
0.010c
0.005s
103
DEEP-BLUE MAXIXE-TYPE COLOR CENTER IN BERYL
o
F
o
I
o sl
s
P
3 oN(o
oo
n@
tl
-TYPE
MAXIXE
B E R Y L* 5 9 0
I
I
{o
q
@
(o n
m
to
lo
lo
tl
td
o
z
I
@
n
N
F
I
I
o
N
@
I
o
d)
@
o
tD6
t@
a
o
no
O\i
(Do
oo
tl
1917MAXIXE
B E R Y L# 5 9 1
n
n
o
I
o
(o
l l
I
n
o
o
H
o
o
o
N
@
@
o
(o
o
I
(o
N
6
I
5000
4000
o
n ;:to
o '-l'
o
I
hour, the sharp line spectrumdisappeared(b), and on
further heating to 400oC for a half-hour the absorption edge near 4000 A was shifted toward shorter
wavelength(curvec). We could then restorethe sharp
line spectrumreversiblyin the heat-bleachedmaterial
by any of three irradiation treatments. Curve (d)
shows the spectrum after Co6ogamma-ray treatment
(29 hours : 20 megarcds); curve (e) after X irradiation (24 hours, 30 kV, 35 Ma, 3 cm distance);and
curve (f) after neutron irradiation (5 min : 3 X 10"
neutrons,/cm').Curve (g) shows the bleachingof the
sharp line spectrum with daylight. Here some of the
material as received-i.e., having the absorption
shown in curve (a)-was exposedin a south window
for one week to daylight with sun, whereupon it lost
the characteristicMaxixe-type absorption.
A simrlar set of experimentswas carried out with a
@
@
F
@
n
o
I
ln
IN
lo
I V A X I X_ET Y P E
G R E E NB E R Y L
+590A
IF
g
I
tLl
7000
6000
I, ANGSTROMS
( g ) c n r e r uM A T E R I AoLF ( o )
A F T E RI W E E KI N D A Y L I G H T
WITI]SUN
8000
(. fO) FA F T E RN E U T R O NI R R A D I A T I O N
H E A T B L E A C H E DI V A T E R I A L
ray'at
beryl,ordinary
of MaxixeandMaxixe-type
FIc.2 Spectra
300K and t0 K.
o
z
difficult at times to apply this test to aquamarines,
particularly to pale green ones, but the absorption
causing the intense blue components of color in
Maxixe-type material is always carried by the ordinary ray.
No Maxixe-type optical absorption was found in
our previous study of 79 beryl crystalsfrom various
localities,and none has beenreported in the literature
sincethe early reports on the l9l7 material published
in the 1930's. Its rarity, and the sudden flood of
material recently,has lent considerableweight to the
initial hypothesisthat irradiation was involved in its
I. e
O)FA F T E R X R A Y I R R A DI A T I O N
H E A T B L E A C H E DM A T E R I A L
@
E
o
( d ) A F T E R G A M M A - R A YI R R A D I A T I O N O F H E A T B L E A C H E DI V A T ERIAL
( c )H E A T E D
To 40o'c
(b)HEATED
ro 20o"c
r) as
RECEIVED
production.
Bleaching and irradiation experiments
A green Maxixe-type specimen was subjected to
the seriesof experimentssummarizedin Figure 3. In
the bottom curve (a) is shown the spectrum of the
material as received.After heating to 200'C for l/2
40oo
6000
X ANGSTROI\4S
8000
Frc 3 Spectraof greenMaxixe-typ"U".ff showingthe effectof
light, heat,and irradiation;ordinaryray.
NASSAU, PRESCOTT, AND I4/OOD
M A X I X E- T Y P E
B E R YL
BLUE CUT STONE
*592
(1974) has studied a blue Maxixe-type beryl and a
similarly colored irradiated beryl (initially pink) by
paramagnetic resonance techniques, and suggests
that trapped hydrogen may be involved in the formation of the color center. He did not. however. investigate the question of whether the center he
studied was responsiblefor the optical absorption or
merely associatedwith it, and further work seemsto
be required on this point.
There appears to be no direct correlation between
the occurrence of the Maxixe-type color center and
the alkali content of the crystal. In previous reports
we have shown that a rough estimate of the total
alkali content of beryl can be derivedfrom the intensity of the infrared absorption between I pm and 2
pm due to water associatedwith alkali (Wood and
Nassau, 1967, 1968).The alkali content of l7 of the
specimenslisted in Table I was estimated this way,
and is given in the last column in the table. From the
fact that, for example, ff446has low alkali (- 0.01%)
but is fairly strong Maxixe-type,while 1594 has high
alkali (- 0.5Vo) and about equally strong Maxixetype, we conclude that alkali is not involved in the
color center directly. The original 19l7 Maxixe
specimenwas high in alkali content (- 0.58o).
The processof the formation of the color center
during gamma irradiation was followed by measuring
the specific absorbance(a : l/l logroIo/1, / being the
( e )A F T E R
GAMMA-RAY
IRRADIATION
OF HEAT
BLEACHED
MATE R I AL
( d )A F T E R
NEUTRON
IRRADIATION
OF HEAT
BLEACHED
MATERIAL
UJ
(J
z
(D
( c ) H E A T E DT O
400"c
U)
( b }A F T E R
l W E E KI N
DAYLIGHT
WITH SUN
(o) AS
K
6000
\, alrosrRous
FIc. 4. Spectra of blue Maxixe-type beryl (cut stone immersed in
carbon tetrachloride in quartz cell) showing the effect of light,
heat. and irradiation: ordinarv rav.
o
deep blue facetedstone, and the resultsare shown in
Figure 4. In this casethe neutron and gamma ray irradiations were longer (15 min - l0'. neutrons,and
l2 days : 200 megaradsCo60).The fading from exposure to one week of daylight with sun (shown in
curve (b), Fig. a) was similar to that from exposureat
room temperature to a 100 Watt tungsten filament
light at a distanceof l5 cm for two weeks.The results
from the green material and the blue material are
very similar, the principal differencebetweenthe two
being the position of the short wavelengthabsorption
edge.
From the absenceof transition elementimpurities,
the ease of decoloration with light or heat, and the
recoloration with a variety of penetratingradiations,
we conclude that a color center is the cause of the
Maxixe-type optical absorption features.Andersson
=
?
r.z
o
z
<
1.O
F
o^
o>
@<
E
!, o.e
t,E
u2
a-
?P o.e
pe
o
*
o.e
I
r
o
U
"-
o.2
DOSE IN MEGARADS
roo
150
Ftc. 5. Development of Maxixe-type blue color in beryl rt446dttri n g g a m m a - r a y i r r a d i a t i o n ; p o i n t s e x p e r i m e n t a l ,l i n e t h e o r y .
DEEP-BLUE MAXIXE.TYPE COLOR CENTER IN BERYL
105
tained (Fig. 7). However, unambiguous resolutions
could not be achievedat the other temperatures,and
it was therefore not possible to obtain activation
Saturataon
coloration
HaIf
Specimen
Coloration
energiesfor the decoloration processes.
cmax
Dose
DesigTrme
Gamma irradiation produced a number of changes
nation
at 6900 A
Ly72 days
d172 negarads
in featuresof the absorption spectra other than the
446
L.46
2.75
1.93
4.0
Maxixe-type bands. The heat-inducedconversionof
596
r.92
597
4.2
70.6
green
beryl to blue beryl (commonly usedto improve
598
2. 2 2
6.0
100.8
the value of aquamarine) by the shift in the absorption edge near 4000 A to shorter wavelength was
used.The change
thicknessin cm) at 6900 A in the ordinary ray as a reversedby the various irradiations
of
Fe'+ in the octhe
conversion
is
due
to
heating
on
function of irradiation dosage.The calculatedcurve
(Wood
(colorless)
(yellow)
Fe2+
to
Al
site
tahedral
which best fits the experimentalpoints in Figure 5 is
-this
change,
reverses
Irradiation
1968).
Nassau,
and
1.46
computed using the saturatioli value of a^ *
and a half coloration rime tr12: 2.75 days (or half as can be clearly seen in Figure 3.
Another set of changeswas seenin the water abdosedrlr: 46.2megarads)in the exponentialcoloralines,a number of which were intensifiedby
sorptions
tion expression:
irradiation. As one example, the c,rspectrum line at
---gse:- : 0.301t/ttrz : 0.301 d/dvr,
13,900A 1l,ZOOcm-1 in Figure 3 of Wood and Nas1og10
4
d-""
sau. 1967) increasedfrom a : 0.26 to a : 0.56 on
: 0.38 on heating
where a is the specific absorbance at 6900 A after I 7-ray irradiation, and revertedto a
for five hours at 250'C. Other lines which increased
days (or d megarads)of gamma ray exposure.
This behavior is indicative of a single type of were in the e spectrum at 22,260, 22,590, 22,720,
this
coloration processin which the rate of development 23,640, and 23,760 A. We have not studied
to
be
not
appear
but
it
does
phenomenon
in
detail,
of color centers is proportional to the number of
color
Maxixe-type
of
the
formation
related
to
the
precursorcentersremaining to be converted to color
centers.It showsthat only a fixed amount of the color center.
Immediately after neutron irradiation of specimens
center precursor is presentin the material. Different
and 592, considerableinducedradioactivity was
#590
saturation
not
different
only
specimens showed
colorationsdue to differentprecursorconcentrations,
100
but also different half coloration times, indicative of
;
different absorption cross-sectionsfor the gamma G
e
rays (Table 3).
z
The blue irradiated material showed a slightly P e o
I
smoky color, and heating to as little as l00oC for a
q
few minutes removed this smoky hue. Although
2
readily seen by the eye, this change was not suffi- EF
v) ad
ciently large to be visible in the absorption spectrum z
and was not further investigated.
o
The process of the heat-induced decoloration of
the Maxixe-type feature (in the absenceof light) was < 4 0
studiedat various temperatures,as shown in Figure 6
z
where the fraction remaining of the original color is z
=
plotted against time at the elevatedtemperatures.A
U
E
temperatureeven as low as 125oCgave a rapid initial
x20
J
bleaching followed by a much slower stage, a I
behavior indicative of a processinvolving more than s
one mechanism.At 200"C rapid fading was almost
o
complete in 30 minutes. An attempt was made to fit
or23
TIME IN HOURS
the curvesof Figure 6 to exponentialcomponents;in
the caseof the 164'C a good resolution into compo- FIo. 6. Loss of Maxixe-type blue color in beryl rt446on heating at
different temperatures; percent color = 100 a/ao'
n e n t sw i t h h a l f l i v e s o f 1 0 m i n a n d 9 6 m i n w a s o b -
TesI-n 3.
Gamma Ray Coloration Rate Parameters for MaxixeTvoe Bervls
I
@
F
v v
106
NASSAU, PRESCOTT,AND WOOD
6
M A X I X E - T Y P EB E R Y L# 4 4 6
T E M P E R A T U R =E 1 6 4 " C
E
F
a
o
z
^vc
o
(o
F^
{
no
E>-
oC
d<
,,' Z
S L O WC O M P O N E N T
itrz = 96 ttttN
oylx = O 58
gF or
ffe
o
a
(D
<
o05
L
O
U
(L
6
FAST COMPONENT
t1l2 = 10 MIN
a64x = 0.68
(morganite)mined in Barra de Salinas,Minas Gerais,
Brazll, but the process was not disclosed. Guso
and Williams (unpublished;Argonne National Laboratory) have irradiated six colorless beryls from
Rhodesiaand also obtained deepblue material which
faded rapidly.
W e h a v ef o u n d t h a t t h e o r i g i n a l l 9 l 7 M a x i x e b e r y l
also faded rapidly on heatingor on exposureto light
(Fig. 8). Here again irradiation resulted in the reformation of the blue Maxixe color center,but in addition the absorption edge at 4000 A also shifted,
resulting in a green color. It is not clear ifthe valence
changeof the iron ion at the low level presentin this
crystal is adequateto account for the absorption edge
shift. It should be noted that even the relatively pale
blue color initially present was not completely
restoredby l5 minutes of neutron irradiation (Fig. 8)
so that apparentlythis material has a low absorption
cross-sectionfor the Maxixe color center,but a hieh
o02
1917MAXIXE BERYL
BLUE #59I
ool
T I M E( M I N U T E S )
( e ) A F T E RG A M M A - R A Y
IRRADIATION
OF
HEATBLEACHED
M A T ER I A L
F I c . 7 D e c o m p o s i t i o n o f t h e l 6 4 o C h e a t - b l e a c h i n gc u r v e o f
F i g u r e 6 i n t o t w o e x p o n e n t i a l c o m p o n e n t s ;p o i n t s e x p e r i m e n t a l ,
lines theory.
present.After one week the only abnormal radioactive speciesrevealedby gamma-ray spectroscopyin
both sampleswas cesium-134,which does not occur
in nature, and has a half-life of about two years.It is
a result of neutron capture by the cesium-133commonly present in small quantities in much beryl
(Deer, Howie, and Zussman, 1962).A checkof all the
other specimensof Table I in the as-receivedcondition indicated that three of the deep blue facetedgem
stones had a low level of cesium-134radioactivity
(about 3 X l0-s microcuriesin specimens#618, 629,
and 638). Accordingly it is clear that some cif tnis
material had definitely been neutron irradiated; it is
possiblethat some or all of the rest may have beenirradiated with gamma-rays,X-rays, or other suitable
treatment to develop the Maxixe-type color, since
thesetreatmentsleaveno other evidenceof their use.
That this material did not come from the Maxixe
mine is ostablishedby the differencesin the spectrum
as seen in Figure l.
A recent account (Bastos, 1975) states that
Maxixe-type beryl can be made from pink beryl
( d ) A F T E RN E U T R O N
I R R A D I A T I O NO F
HEATBLEACHED
M A T ER I A L
U
O
z.
dl
TE
U)
dl
( c ) H E A T E DT O 4 O O ' C
( b ) A F T E R5 D A Y S
IN SUN
(o)AS
RECEIVE
2000
4000
6000
8000
}., ANGSTRoMS
8 . S p e c t r ao f l 9 l 7 M a x i x e b e r y l , s h o w i n g t h e e f f e c t o f l i g h t ,
heat, and irradiation; ordinary ray.
DEEP-BLUE MAXIXE.TYPE COLOR CENTER IN BERYL
107
cross-section for the reaction producing the edge that irradiation did not produce the Maxixe color
center in nature but that it was formed in some other
shift.
geological
way during the growth Process.
is
that
What can be deduced,however,
not
have
could
time
of
formation
since
the
irradiation
Acknowledgments
causedthe blue Maxixe color center, since it would
presence
green
to
the
produced
due
a
color
have
also
We wish to thank Mr. R. Crowningshield of the Gemological
of the yellow component (indicated by the short Institute, New York City, for arranging permission for us to exwavelength absorption edge near 4000 A). Irradia- amine many of the stones, for early communication of the results
h e l p f u l d i s c u s s i o n sM
; r. B. W.
and
t i o n p l u s s u b s e q u e n t h e a t i n g c o u l d n o t h a v e of someof his experiments, for
Anderson of the Laboratory of the London Chamber of Comproduced the blue color of the original Maxixe either, merce, England, for the loan of the original Maxixe specimen; Mr.
since the blue color center bleaches at a lower H . R u b i n o f t h e G e m s e tC o m p a n y , N e w Y o r k C i t y , f o r t h e l o a n o f
temperature than that required to remove the yellow the green Maxixe-type cut and rough stones. We are grateful to
component by a shift of the absorptionedge(seealso S. S. Voris for performing some of the gamma ray spectroscopy;
M. Bowden for some of the gamma ray irradiaFig. 3). Accordingly it would appearthat the Maxixe E. R. Schmid and
t i o n s ;J . W . M i t c h e l l a n d J . E . R i l e y , J r . f o r t h e n e u t r o n i r r a d i a t i o n
color center as seenin the 1917beryl specimensfrom e x p e r i m e n t s ;a n d R . G u s o a n d J . M . W i l l i a m s f o r t h e r e s u l t s o f
the Maxixe mine must have been formed during the their unpublished experiments.
geologicaf growth process by a specific set of growth
References
conditions and not natural irradiation. No information is availableconcerningthe nature ofthese condi- ANonnsoN,B. W. (1956)The spectroscope
and its applications
in gemmology;part 34. Gemmologist,25'103(June 1956).
tions.
Summary
A deep blue color center is produced in beryl by a
variety of penetratingradiations.If the original beryl
is yellow or green, the resulting color can be a green
or blue-green.This color centercannot be induced in
just any beryl, and the nature of the required precursor is presently unknown. It does not appear to involve transition metals, alkalis, or water.
The color center is best characterized by the narrow absorption bands in the ordinary ray only, giving
a quick test by examination in polarized light. Two
variants exist. One, termed Maxixe, is found in the
original 19l7 Maxixe material which occurred
naturally. The second, termed Maxixe-type, can be
produced in a significant fraction of irradiated beryls
of random origin, and there is here no clear evidence
for a natural occurrence.
Both light and heat exposurecan causea complete
fading of the blue component of the color, and it can
be again restoredby 7-ray, X-ray, or neutron irradiation in the Maxixe-type material. In the caseof the
initially blue l9l7 Maxixe material, irradiation of the
bleachedmaterial produces a green color, indicating
ANosnssoN,W. O. (1974) EPR of HydrogenAtoms in Beryl
Crystals.CongressAmpere,Nottingham,England,September,
l9'7.4.
BAsros, F. M. (1975) Maxixe tYPe beryl. Lapidary J. 28,
t540-1542.
CnowNtNcsnten,R. (1972-3,winter) Dark blue aquamarine.
G e m sG e m o l 1. 4 . l l l - 1 1 2 .
DEER.W. A.. R. A. Howts, lNo J. ZusslleN (1962) Rock'Forming
Minerals, Yol. I Ortho- and Ring Silicates (Beryl' p. 256-267).
John Wiley and Sons, Inc.; New York'
N A S s A U ,K . ( 1 9 7 3 )T h e e f f e c to f g a m m a r a y s o n t h e c o l o r o f b e r y l ,
smoky quartz, amethyst, and topaz. Lapidary J. 28,20-40
-,
AND D. L. Wooo (1973)The nature of the new Maxixetype beryl. Lapidary J.21' 1032-1058.
Roesr-tNc. W.. lxo H W. TnonNru (1935) Maxixeberyll. ll.
Zentralbl. Mineral. Geol. Pal'dont. 1935 A' 134-139.
S c H r - o s s r . t l c t t E nK, . , e x n H . K I - l N c ( 1 9 3 5 ) D e r M a x i x e b e r y l l . l .
Zentralbl. Mineral Geol Paldont. 1935 A' 37-44.
W t l o , G . O . ( 1 9 3 3 ) M i t t e i l u n g i i b e r e i n a n s c h e i n e n dn e u e sB e r y l liumsilikat. Zentralbl. Mineral. Geol. Paliiont 1933 A' 38-39.
W o o D , D . L . , l u o K . N n s s n u ( 1 9 6 7 ) I n f r a r e d s p e c t r ao f f o r e i g n
molecules in beryl. J. Chem. Phys. 47,2220-2228.
-,
( 1 9 6 8 ) T h e c h a r a c t e r i z a t i o no f b e r y l a n d
AND emerald by visible and infrared absorption spectroscopy. lz
Mineral. 53, 777-800.
receiued March 3, 1975; accepted
for Publication, June 12' 1975'
Manusuipt