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,**.  -  +2  ,**.  3  3 Color Change Measurements of a Scoria and Simulation Heating Experimentsby Spectro-colorimetry
Yuta YAMANOI῍,῍῍, Satoru NAKASHIMA῍,῍῍, Satoshi OKUMURA῍,῍῍and Shingo TAKEUCHI῍῍
In order to study quantitatively color changes of basaltic scoria erupted at Takatsukayama, North-east Izu,
Japan, the scoria colors were measured by spectro-colorimetry and described in the international standard color
space (CIE L* a* b*). The color values [a* (red) and b* (yellow) values] of Takatsukayama scoria cone
increase from margin to center, indicating their color change from black to red. The bulk chemical compositionsof scoria, including total Fe content, remain almost unchanged despite the color variations. On the other hand,
the FeO (Fe,) contents determined by the phenanthroline method have a good linear relation with a* values(red) of scoria. Under the optical microscope, the red parts are not found in the black scoria, whereas the red
scoria have red parts in the groundmass and the olivine phenocryst. For dull red scoria, the red parts areobserved only in the groundmass. These indicate that red parts appear ﬁrst in the groundmass and then in theolivine phenocryst. Visible and Raman microspectroscopy indicated the presence of hematite in these red parts.
A series of heating experiments of the black scoria under an atmospheric condition at /**ῌ++/* wereconducted to simulate the color changes of Takatsukayama scoria. The heated scoria showed the increases in a*and b* values (i.e. red coloring). The FeO (Fe,) contents of the heated scoria had similar linear correlation
with a* values (red) as for natural ones. The presence of hematite was also found by visible and Raman
microspectroscopy.
These results imply that the increases in a* and b* values (red coloring) of Takatsukayama scoria can be
explained by the high temperature oxidation of Fe,, resulting in the formation of hematite ﬁrst in the groundmass
and then in the olivine phenocryst. Since the direction of the red coloring is oblique to the depositional sequencesof the cone, the high temperature oxidation process might have occurred after the scoria deposition from the centerof a heat source to the outer parts.
Key words : color, scoria, spectro-colorimetry, oxidation, hematite+ῌ ῐ ῎ ῑ ῏

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Interactive Research Center of Science, Tokyo Institute of Technology, O-okayama ,ῌ+,ῌ+, Meguro-ku,
Tokyo +/,ῌ2//+, Japan.
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Department of Earth and Planetary Sciences, Tokyo
Institute of Technology, O-okayama ,ῌ+,ῌ+, Meguroku, Tokyo +/,ῌ2//+, Japan.
Corresponding author : Yuta Yamanoi
e-mail : yuta@geo.titech.ac.jp`¹abD+X ºD»c dDe-f¼

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Takatsukayama Volcano from Koyama et al.
(+33/) with locations (Point+ to 0) for color
measurement and sampling in this study.
Numbers in parentheses are distances (m)between these locations by trigonometricalmeasurements. Based on duplicate measurement of distance between Point+ and Point,, theerrors are ¡/ m.

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Fig. ,. L* a* b* color space (CIE +310) used in thisstudy for quantitative description of scoria
colors. The L* value is the psychometricbrightness and corresponds to black (L*f*)and white (L*f+**), and the a* and b* values
are psychometric chromaticness. Plus value ofa* corresponds to red color, minus one to green.
Plus b* value corresponds to yellow color,minus one to blue.

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Table +. Experimental conditions and analyzed
samples by XRF and the phenanthroline
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BX/*), a dispersive spectrometer with - grating
monochromators (Acton Research SP-*0) and a
CCD detector (Andor DV.,*-OE). The dottedgray arrow is the light pathway for measuringvisible absorption spectra under the microscopeby using +/* lines/mm grating (.**2** nm).
The gray arrows are the light pathway formeasuring Raman spectra with /+../ nm Ar
laser excitation by using +,** lines/mm grating(+**,+** cm®+).

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Fig. .. Colors of scoria measured at the outcrop in
Fig. + plotted in an a* -b* -L* diagram. Since
DE*ab[(DL*,ºDa*,ºDb*,)*./] is smaller than*.*-, the errors are within symbol sizes. The L*,
a* and b* values increase from point0 to point+.

Fig. /. Colors of scoria powders sampled from theoutcrop in Fig. + plotted in an a* -b* diagram.
The L* values are /*/ for all the samples.
The error bars represent a standard deviation(+s). The a* and b* values tend to increase
from point0 to point+.

322



Fig. 0. Spatical variations in colors of scoria sections. Since DE*ab[(DL*,Da*,Db*,)*./] is smaller than*.*-, the errors are within symbol sizes. The L*, a* and b* values increase from point0 to point+. They
increase from the interior to the scoria surface.

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"K Point+  Point0 + LMNO&P6 a* -b* Q" Fig. 2 K+ >./01cd+RSTUVWX"K b*  a* ( 4Y ¡¢" Fig. 3 K+ ]£¤./01t|&Z b*ῌa* +7[\[\ "K ]

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6rWsWtyz°

v56t|·6t|hi_= Point/  Point0  ¶ 6rWsWtyz·6t|¹hi_=

Fig. 1. Temporal changes in the L*, a* and b*
values for the heated scoria powders (starting
powder from Point0). The errors are standard
deviations (+s) and are within symbol sizes.
All the a* and b* values increase with theheating time.

Fig. 2. Variations in colors of heated scoria in an
a* -b* diagram. The errors are standard deviations (+s) and are within symbol sizes. The
ratio of b* to a* (b*/a*) is dependent on theheating temperature.

324

 Fig. 3. Back scattered electron images of red and black natural scoria and X-ray (Fe) intensity maps. (a) Red
scoria sampled at Point+ : (+) low magniﬁcation, (,) high magniﬁcation, (-) X-ray (Fe) intensity map at thesame high magniﬁcation as in (,). (b) Black scoria sampled at Point0 : (+) low magniﬁcation, (,) highmagniﬁcation, (-) X-ray (Fe) intensity map at the same high magniﬁcation as in (,). Ol, Pl, Cpx and Fe-Ti
represent olivine, plagioclase, clinopyroxene and Fe-Ti oxide, respectively.

'%S)* 




 Point, 






!

=-Sx»¼78
Sx L z{)* /+, nm
P|


"#

325

B

l%mL k&)tnoBFeO I NFe

,p

Fe,p

}mL 

}m0 FeO ~ῌ O.ῌ-ῌ, 

PQL ST0 Table . 12 ^L $% X &'()*  +,-./0 Table - KL V `"* a* T NVQ  FeO (Fe,p)12 3 Point

45 )6789/: +,-.

/;<=->?@A<
GHIJKL

B

B CDEF

SiO,L +M NFe, O- O

PQL TiO, IR2*ST L* T NUQL a* T NVQL
b* T NWQ=-0 Fig. +* 12 

SiO,L +M NFe, O- OPQL TiO,

BI L*, a*, b* T,, jMI k&0 Fig. ++ (a) 12 /+, nm&XYs"tL u

FeO (Fe,p)~ῌ ST a* T XY0 Fig. ++ (b) 12 
w

-./

*`a JB--FeO I Sx  Imai et al. (+33/) )*
FeO I 0 FeO I 2*L *.-0ῌ

"* a* Ts2*A B
T B^_L `a b@c?defghig)*%m`a noB

B

FeO (Fe,p)Is[\r&2* @L 45 

XY<Z[\]"*.ῌ-ῌ-I XY0*?L

V-

Fe

,p

l

I (ppm) qrk&vw,B

Fe

,p

x

*usy*u01*a*

FeO (Fe ) I XY Nr&Q,p

L 789/: A * bL a* T
s +/  V L ] a* TR
45 FeO (Fe,p) Is789/: A)ty.ῌ-ῌ. 

45 789/:B gg
(Table ,) L  ¡¢%l£¤¥h¦Table ,. Description of colors of phenocrysts andgroundmass for the sample thin sections underan optical microscope.

Sx0§# gg¨' +* ©

R:ªg«0L ¨' +** © R:ªg«0 4
5 789/: ggV¨L 45 ¬ ¨L 45 789/: V¨L )645  ­¨ ®¯<¡¢%l£¤¥h¦0 Fig. +, 12 45gg¬ ¨ (Fig. +, (a) (-)) °±¨' N.** nm Q l%ms2*²±L  #l£³s ´µL 789/: ggV¨ (Fig. +,(a) (,)) L ¶·¸¹ N.**º//* nmQ l£³s@Table -.

Chemical compositions of natural and heated scoria powder samples.

326 

jklmnocp qors touvwx
 (Fig. +, (a)(+))  .**nm! "#$%&' 

//*LM56789:;< (Fig. +, (a) (+), (,)), NO (Fig. +, (a) (-)),()( (Fig. +, (b) (+), (,)), CP) (Fig. +,(Fig. +, (b) (-)) *+ ,-./012"#%&(b) (-)) QRSTU V >?@ABE Fig.

' 34+  ( (Fig. +, (b) (+))+- FG WK+ X'K V YZA[\@]^

56789:;< ( (Fig. +, (b) (,)) *+(cm-+) 5_`aE Table / FG bc O def .** //* nm! "#$%&' =',-."#>?@ABCD+5 (

+ EFG .** //* nm! "#$%HIJK

Fig. +*. Relationship between the L*, a* and b*
values and the SiO,, total Fe (as Fe, O-) and
TiO, contents in the bulk rock. The solid
symbols represent the results of heated scoria
and the open symbols represent the results ofnatural scoria. The bars represent maximum
standard deviations (+s). The bulk chemicalcompositions of scoria remain almost unchanged
despite the color variations.

Fig. ++. (a) Absorbance at /+, nm (Abs/+,) as afunction of Fe,g concentration (ppm) for
solutions of standard rock samples determinedby the phenanthroline method (Fritz and Popp,+32/). The regression line gives the relation :Fe,g (ppm) h /.0 i Abs/+, g *.+*.
(b)
Relationship between a* values and FeO
contents (wtῌ) in the scoria powders. The
circle symbols represent the results of natural
scoria. The cross symbols represent the resultsof heated scoria. The error bars of FeO
content (wtῌ) are based on these for the
standard rock JB--. The error bars of a*values represent standard deviations (+s).
Both the natural scoria and heated scoria show
the similar linear relation between a* values(red) and FeO contents.

C]= &XYZ=¯°][012»¼34
Table .. Iron contents and color values : Absorbance at /+, nm, Feand b* values of natural and heated scoria powders.

 T  .  Si  Al 



,º

327

and FeO contents, and L*, a*/][P " k^ ry Hart et al. (+310), Kolesov and Tanskaya+8][)*]=k  :

(+330), de Faria et al. (+331), Sharma et al. (+331) = ][^]=k ? L* kI  Nagao andC]  !"Nakashima (+33+ ; +33,)  ./s\# $%& !"#'()* + ,-./01234567

p][ &XYZhij][de][ &XYZo0$ 8*9 :; <=> ?.**@//* nme][0&XYZhij][ Point0 ab

ABCDE FGH ; Fig. +, (+), (,)I Point+ 0 a* 0 b* k00; L* k;n1^

y0#b*:0 dOP

&JKL (Fig. +- (+), (,))  Fe, O- ?<MNI op][ L* k /*/ 0O[k#'()* OP Q

 : y*b][P9 :b* 

R=>9S$T=> (Fig. +, (-)) &JK?./ jC]=][0./L (Fig. +- (-))  Fe, O- ?<MNI  j  )b ¡¢ £I # ¤
L* k¥¦

'()*"§#¨a©b* de][0&XYZhij][ª L* k g « ¬­/ /ῌ+ 

®
^a^"#b op L* k#O[++

UVW&XYZ=[\!][^_` Point0

Point0 ab Point+ ca: a* 0 b* k#n1^:9

ab Point+ ca: de][0fg^&X y a* 0 b* k¯°&XYZ{±!"¯°

YZhij][ &XYZ L* k ?lI a* k?<=°I ^:?<I b* k ?mI #n1^ + fg^&XYZ

][0op][_` ²³kw^"op][ a* 0 b* k#n1

; a* 0 b* k¯°qc£^ © deqc#

)b 9r /@+* cm s&XYZh

jab

0b*

{|}de][./=¯°qca´©µ¶tuca: L*, a*, b* k#vw^: xy0#za{|} ~Ofg^./]=k# .

/ῌ, 

T=&XYZ·¸¹12y0: a* k  {328  b*   (Fig. 1, Fig. 2).

(+33/)  

- n /**y1**M n 2 opz{ Point, n 1**M n 3y+, op+,-./)&!"# $%&'()*01$%&2 345

678!9*(+33/)!:%$;<=> ?@ 

 +***M z|I} ++/*M ~n +y, op
6

r!fK>&st=>&VWB!uv $%&2 9e$ ?@ BCdB&%ABCDE 1FG!HIJK> 2 L 

?O 6!9& a*  b* +,+/*M  678!:%$"#NJK> +PQ_&+)&2"#?O 6PQR&+S;<$ Point+ BC !9e$345 BCOop01r! VW 678#YS%$%& 9*1FG!

$%&2
TUVWBX1#Y (Table ., Fig. /) 

TU BCOopS01_&!

678Z[\BX1#Y (Fig. 2) S]^_&

9*TU!/% S% 78SG!

` Point  a*  b*  Point0 aba*  b* c%dB

6!9e$fK> a*  b* ghiD_&jR&2 klm Point.  a*  b*  Point0 Sn /**M  , op9*(q%op 6

r!f

K>&st=>&VWB!uv_&2 wx! Point

Fig. +,. Typical visible spectra for the scoria thinsection. (a) Olivine phenocryst : (+) red partof natural scoria, (,) red part of heatedproduct, (-) pale green part of natural scoria.
(b) Groundmass : (+) red part of natural scoria,(,) red part of heated products, (-) black partof natural scoria. Absorption bands (.**y//*nm) in the red parts of natural scoria (+) andheated products (,) are similar to those ofhematite (a-Fe, O-) (Nagano et al., +333 ; ,**,).

Fig. +-. Typical Raman spectra for the scoria thinsection. (a) Olivine phenocryst : (+) red partof natural scoria, (,) red part of heatedproduct, (-) pale green part of natural scoria.
(b) Groundmass : (+) red part of natural scoria,(,) red part of heated product, (-) black partof natural scoria. Assignments of Raman
bands are after Hart et al. (+310), Kolesov andTanskaya (+330), de Faria et al. (+331) and
Sharma et al. (+331). Solid arrows in (a) (+),(a) (,), (b) (+) and (b) (,) indicate Raman
bands due to hematite (a-Fe, O-). Dottedarrows in (a) indicate Raman bands due toolivine and those in (b) indicate Raman bands
due to glasses. Raman spectra in the red partsof natural scoria (+) and heated product (,)
have Raman bands due to hematite (a-Fe, O-).

,'( !"#$(1'>*  b*ῌa* 329

C: .**//* nm 9 C
Nagano et al. (+333 ; ,**,) RS Fe, O- Z[ /ῌ- 

»¼WX



j\  ,!a Z//* nm @

 !"#$%& Point '() (Table ., Fig.
/) *+, X -. /0123456 (Table -,\ *NS  : w`!a (Fig. +- (+), (,))

lS?: Fe, O- Z[jFig. +*) *789*: /01234;<=> ?

\@@AB'()CDA@ E : FGHI Fe, O- Z[j\ w` lS:   ¡JK/ Fe, Ti LMEw`Rt

Y4

N?OPQ

N¢£¤SC: Fe, O- Z[j\ 

RS = : TUV *WXY4  a* ) Z[\ *Y4 ¥S5y ¥S¦§RS*rs]^_`ab#`  FeO (Fe ) LR (Turrell, +330). Nt: v`w`xy*x,c(Fig. ++)

7Q*: a* )* FeO (Fe,c) *d -e fSgh~[((C Fe, O- Z[j\ Y4¨*rs

QR +, X -. i: /jL C9kR v`w`xp1R* Fe, O-

!"#$ lS;<=>: FeO (Fe ) L

Z[j\ Y4R*C: McKernan and Carter1C Fe,cῌtotal Fe 1*;<-ehm(+323) 56*© ªt: Point+ «¬Nta* )o \ C[(!"#$uv`w`x lSC: z*{R ,c : !"#$[(1 ZnFe,cp1 (Fe qFe ),c

TU!"#$*-c?*rsR

Nt!"#$uv`w`xy jL SRli (Fig. 3a), v`w`xCn zFe, O- Z[j\ Y4

C: z*{R  [(7|}?*|t

RS*rsR x~ lSC­t®

S?*: x~ C[(*(Rt¯°±£@t: x~ v`w`x:(Table ,). : !"#$[(1Cv`w`xy²³´x: jµ¶`p1 Lj ·w!uj*x~[(1*rsR

p1 i Fe,O- Z[j\ Y4RS*rs

TUV lWXY4 v`w`xy[(*x~[( !a (Fig. +, (+), (,))

Table /.

R¸¹i: !"#$ a* ) Z[\ * b* ) Zº\ oResults of Raman spectroscopy for natural and heated scoria thin sections.

U&¸NOVP ¹VºQ RVS:»¼

330      Fe,  Fe-  !
Fe, O- " # $%&'()%*+,-%.
/ῌ. 

 /012

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0 



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7? U/012+,7 ! ^[7!&. ^kl >8,67

3 45(Table

n<&.

,) 6,

Point0 6, Point+ /0127

89: ! ;8(

29( )*(8-789F !98%. <9 /012 Fe, zh 6, 7`6<9\`7 a* ! Fe-  b* ! _ $A$%]`)%. U/012: Fe, 

=7>? @7 Fe,

>%*+,-%. ABC# (+ U/012zh  L* ! ; a* !  b* ! _: (Fc c : D>-,!#8 d8.

DE,7F 45G-&. >-,/**+***L 7i%<(A7<9HIAJK /**L ,* MN ( U/012( Fe,  OP!9!:<&QR)%.

$%. :& b*ῌa*HI(S(

TUV (+33/) (WX

G-98%Y7 U/012Z[\7!9 7]898% (Fig.+). ^-7!

a*'(( /01

a* !   b* ! _ $A! .(]`j!

DTGcn%.
-  /012 ABC# 8-F 

=>7

()% FeO!   b* ! _ ]` \`( Z[(Fe,) ?+78<fc! a* ! ab!98%. <9 ZM"(

 FeO (Fe,) ?+N7@A,B',-



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a*  b* !#c d Ze7A7%

7<9 a*  b* !$A  ! 8/0.  /012( Oo :7

 45G- ;8(7 

12(f&*+,-%.
/ῌ/   

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&.

45G-%. :& ABC# g%7?&h7i%'((/012)*(P8 U/01

789F 45G-&.
/ CQ/t7?  /0122+,7j!&. ^kl '((ABC# kl6,3 m,n]`;6o>Q 7 .**//* nm  D¡B!&. >-()%j!&. :& U/012+" ^-E¢()%.

kl^pqBCkl-$%>7
? /012.VMN/rstuZ%>Q()%>j!&. HI(

 3  Fe, O-

0 C£/t7? ¤W 7
Fe, O- " >F,n£¥s¡B!&.
1 ¤kl6, /012 a* !   b*

ABC# )*(-v!/012! _ $A 

.VMN/rstuZ<98% we?

   

 Fe,  Fe- 

7x8y(HIPY>7<9 ?qB,n/ ! Fe, O- " G# $%>7%F

012z{|n.VMN/rst G,7

*+,-%. :&/012zZV/}~01Qn%*+,-%.
>-:( U2~07;89*5(

~0>/012 Fe,  Fe- : Fe,  =7>? @7 Fe, 

>%*+,-%.

 ()%8YR,n17D:<98

2 U/012d6, Z& +,n7<9+,n. V MN/[7ab!9? /012ZeA~0rst1Qn%. we G::n;7<9 ¦7x8 Point+ 6, Point0 7`6<9U2y3,7PY>7<9 2

OP! !&F*+,-%.

~0(!&6, 45 6,2VZ:(.VMN/rst6Qn%*+,-%.

§H¨©ªsI«J
L°±7

I«¬9HI­®¯K

G::n²³M8&. ´µ¶·10uPQ·¸¹ºu vk{|»¼§¨


    !
"#$"#% &# '()*+#,-./ 0123456789:;<"#%== >?9;@A%ῌ ῏ ῎ ῍Cas, R. A. F. and Wright, J. V. (+321) Volcanic successions
modern and ancient. Appendix +. Methods used in studying modern pyroclastic deposit. Allen & Unwin, London,.03ῌ.12.
de Faria, D. L. A., Silva, S. V. and de Oliveira, M. T. (+331)
Raman microspectroscopy of some iron oxides and oxyhydroxides. Journal of Raman Spectroscopy, ,2, 21-ῌ212.
Fritz, S. F. and Popp, R. K. (+32/) A single-dissolution
technique for determining FeO and Fe, O- in rock andmineral samples. Amer. Mineral., 1*, 30+ῌ302.
BC DEF GH I+33+J K0 X LMNOPQ.
RSM IῌJ% TUVWXYZ ,, ,2ῌ
...
Hamuro, K. (+32/) Petrology of the Higashi-Izu Monogenetic Volcano Group. Bull. Earthq. Res. Inst., 0*, --/ῌ.**.
Hart, T. R., Adams, S. B. and Temkin, H. (+310) Raman
scattering from phonons and magnons in a-Fe, O-. In
Proceedings of the -rd International conference on Light
Scattering in Solids, edited by M. Balkanski, R. Leite and
S. Porto. Flammarion, Paris, ,/3ῌ,0-.
Imai, N., Terashima, S., Itoh, S. and Ando, A. (+33/) +33.
compilation of analytical data for minor and trace elements in seventeen GSJ geochemical reference samples,“Igneous rock series”. Geostandards Newsletter, +3, +-/ῌ,+-.
Kolesov, B. A. and Tanskaya, J. V. (+330) Raman spectra
and cation distribution in the lattice of olivine. Material
Research Bulletin, -+, +*-/ῌ+*...
[\]4E^_ `aEbc a I+33/J defgh\i h , : jk -, ka lmh\n"% h\ .* +3+ῌ,*3.
McKernan, S. and Cater, C. B. (+323) The growth ofhematite by oxidation of iron-bearing olivine. Ultramicroscopy, -*, ,/0ῌ,0,.
opqrE ost I,**,J u vwxyh\z{|}~ : h\ ,***  2  +2 h\}~ % h\ .1 1/1ῌ10+.

331o EE I+32/J defgh\v7%  +2 +/2ῌ+1..
/ E 3  I,***J h\ uk
E.R %  ,, .-/ῌ.-3.
Nagano, T. and Nakashima, S. (+323) Study of colors anddegree of weathering of granitic rocks by visible di#use
reﬂectance spectroscopy. Geochem. Journal, ,-, 1/ῌ2-.
Nagao, S. and Nakashima, S. (+33+) A convenient methodof color measurement of marine sediment by chromameter. Geochem. Journal, ,/, +21ῌ+31.
Nagao, S. and Nakashima, S. (+33,) The factors controlling vertical color change of North Atlantic abyssal plainssediments. Marine Geology, +*3, 2-ῌ3..
Nagano, T., Mitamura, H., Nakayama, S. and Nakashima,
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