Gem quality and archeological green “jadeite jade” vs “omphacite

jade”: A multi-method study.

Alessia Coccato1, Stefanos Karampelas2*, Marie Wörle3, Samuel van Willingen4, Pierre Pétrequin5

1 Ghent University, Department of Archaeology, Sint-Pietersnieuwstraat 35, 9000

Ghent, Belgium 2Gubelin Gem Lab, Maihofstrasse 102, 6006 Lucerne, Switzerland; e-mail:

s.karampelas@gubelingemlab.ch 3 Swiss National Museums, Collection Centre, Lindenmoostrasse 1, 8910 Affoltern am

Albis, Switzerland4 Swiss National Museums, Archeological Department, Museumstrasse 2, 8021 Zurich,

Switzerland5 Grande Rue 71, 70100 Gray, France

Abstract

Seven gem quality samples of known origin and nine samples of

archaeological importance were studied using Raman spectroscopy in order

to characterize them as jadeite- or omphacite-jade. The results were also

compared with those acquired using other techniques such as classical

gemological, EDXRF, UV-Vis-NIR in absorption, FTIR in absorption and

micro-FTIR in reflectance. Raman spectroscopy confirmed the jadeititic

nature of the five gem quality results as well as the omphacititic natura

of the two. It was also found that two archaelogical samples are jadeite-

jade and seven omphacite-jades. EDXRF and micro-FTIR in reflectance data

acquired on some of the samples confirmed these results. Data acquired

using classical gemology, UV-Vis-NIR absorption and FTIR absorption

spectroscopy were similar on omphacite- and jadeite-jade; thus these

methods cannot used for their separation.

Introduction

1

"Jade" is a trade name which for gemologists refers to two virtually

monomineralic rocks; "nephrite jade" and "jadeite jade". "Nephrite jade"

is an amphibolitic rock consisted of calcic amphibole from the tremolite-

actinolite-Ca2(Mg,Fe)5Si8O22(OH)2- series whereas "jadeite jade" is a

pyroxenitic rock called jadeitite. Jadeitite is defined as the stone

consisted of at least 90% in volume of pyroxene, with the average

pyroxene containing at least 90% in mole in sodic pyroxene jadeite -

NaAlSi2O6-.[1] The homogenous and saturated green colored, semi-transparent

to translucent "jadeite jade" is one of the most appreciated gem quality

"jade"; specifically those found in Burma.[2,3] Additional sources of gem

quality jadeite-jade are also found in Russia and Japan.[1]

Other pyroxenitic rocks with sometimes green to black color and

similar appearance to "jadeite jade" can be found; e.g.,kosmochlor-rich -

NaCrSi2O6-,omphacite-rich -(Ca,Na)(Mg,Fe2+,Fe3+,Al)Si2O6- pyroxenitic rocks.[3,4] These rocks can also contain more than one pyroxene as well as other

minerals.[4-8] Recently have been discovered also some omphacite-rich

pyroxenitic rocks (omphacitite) of fine quality green having similar

macroscopic appearance as well as gemological characteristics with those

of fine quality green "jadeite-jade".[8,9] These similarities raised some

questions about the separation of these two gems; e.g., regarding the

nomenclature of these green fine quality omphacite (sodic calcic)-rich

rocks and whether the term jade should be expanded (i.e., call this gem

"omphacite-jade").[9] In the present article the term jade is used for

both omphacite- and jadeite- rich rocks.

"Jade" materials, are also of interest for archaeologists, as they

were used to produce tools (as well as some adornments etc.) since VI-IV

millennium b.C. and are today found in excavations throughout the world

(from Europe to Far East as well as to Central and South America). [1,10-12]

In archaeology though, the term "jade" has though a broader sense;

including more rocks (not forcibly monomineralic) than in gemology; e.g.,

2

eclogites, serpitinites etc. are also sometimes considered as "jades" or

sometimes referred to as "greenstones".[1,10-14] Nowadays, jadeite-jade and

omphacite-jade is in Italy as well in Russia, Burma, Japan and in Greece.[1,15] However, up-to-date, traces of Neolithic exploration of "jadeite-

jade" is found solely at the Western (Italian) Alps. [14,16,17]

Raman spectroscopy is frequently used for the characterization of

"jade" like materials.[12,18] To the present study, the characteristics of

jadeite- and omphacite- rich samples of fine gem quality are investigated

using strictly non-destructive methods (including Raman spectroscopy), in

order to find their similarities and differences. Additionally, the

characteristics of "jadeite-jade" like archeological artifacts excavated

in Switzerland as well as "jadaite-jade" like rough samples recently

collected directly where "jade" similar to materials sourced during

Neolithic,[19] were studied using similar instrumentation in order to

characterize them.

Materials and methods

Sixteen samples of gemological and archaeological were selected for

this study. Seven fine gem quality green natural color samples were

chosen to be tested; six samples were from Gubelin Gem Lab (GGL)

collection and one (JDXX051) was loaned from a reputable source (see

acknowledgements). Five samples were jadeitite ("jadeite jade") and two

(JDRUS01 and JDXX051) omphacitite ("omphacite jade"). The origin, weight,

dimensions and description of the samples can be found in Table 1. All

samples were studied using "classic gemological" methods; i.e.,

microscope, UV fluorescence reaction under short- and long-wave 6 Watt

lamp excitation (254 nm and 365 nm respectively) and specific gravity

with hydrostatic method with an electronic balance (due to the size and

shape of the samples, refractive index measurements were not feasible).

Sample Provenance

Weight(ct)

Dimensions(mm) Shape/Cut Specific

gravity

3

JDBU001 Burma 2.41 8.10x8.03x4.59

Round/Cabochon 3.37

JDRUS01 Russia 3.45 21.95x15.27x1.57

Leaf/Carved 3.34

JDRUS02_2

Russia 1.41 8.16x6.10x3.23

Oval/Cabochon 3.33

JDRUS02_3

Russia 0.86 8.48x5.54x1.77

Oval/Cabochon 3.35

JDXX002 Burma 1.39 8.08x6.08x3.01

Oval/Cabochon 3.33

JDXX021 Burma 7.30 17.79x10.37x4.26

Oval/Cabochon 3.37

JDXX051 Unknown 4.05 19.58x7.56x3.39

Leaf/Carved 3.33

Table 1: Description and specific gravity of the studied gem-quality samples.

Seven objects (axeheads) of archeological interest found in

excavations carried out in different places in Switzerland were selected

among the Swiss National Museum (SNM) collection as well as two rough

samples (PP10 and PP15_1; see table 2) recently collected by one of the

authors (PP) from Western (Italian) Alps (from sites exploited during

Neolithic). The origin, weight, dimensions and description of these

samples are presented in Table 2. The seven axeheads (A469_4, A810,

A1750_5, A8830, A8831, A8841, A31392, A33853 and A47625; see again table

2) were examined using only the facilities of SNM as it was difficult,

for security reasons, to leave SNM premises. The two recently collected

rough samples (PP10 and PP15_1) were examined at GGL as well.

Sample Provenance Weight(ct)

Dimensions(mm) Description

PP10 Martinion LePo

8.12 27.18x18.63x4.24 Raw materials from Western Alps

PP15_1 Revello Le Po(CN)

0.11 5.71x3.83x1.01 Raw materials from Western Alps

A469_4 Uster (ZH) - 58.1x49.6x13.6 Axehead. Rock.

A810 Zurich (ZH) - 77.0x39.4x20 Axehead. Rock. Oblique edge,

4

.0 rectangular cross section.

A1750_5

St-Aubin (NE) - 48.2x37.6x16.0

Axehead. Rock. Incomplete cuttingedge.

A8831 Luscherz (BE) - 142.0x58.8x21.8 Axehead.

A31392 St-Aubin (NE) - 39.5x35.3x15.4 Axehead. Rock. Rear part broken.

A33853 Meilen (ZH) - 77.3x43.1x17.6 Axehead. Rock. Asymmetric edge.

A47625 Stein amRhein (SH)

- 49.3x34.1x14.0 Axehead. Rock.

Table 2: Description and specific gravity of the studied samples of archaeological

interest.

Raman spectra were also acquired on all gem quality samples, using

a Renishaw Raman 1000 spectrometer coupled with a Leica DMLM optical

microscope, at GGL. All spectra were recorded using an excitation

wavelength of 514 nm emitted by an argon ion laser (Ar+) and most were

taken using standard mode (with ×50 magnification). Raman spectra were

acquired from 200 to 4000 cm-1 using a power of 5 mW on the sample, with

an acquisition time of 60 seconds (3 cycles) and about 1.5 cm-1

resolution. Rayleigh scattering was blocked by a holographic notch

filter, the backscattered light was dispersed on an 1800 grooves/mm

holographic grating and the slit was set at 50 μm. Spectra were obtained

also with a Horiba Jobin Yvon (LabRam Aramis) spectrometer coupled to an

Olympus metallurgical microscope, on samples of Table 2 at SNM. All

spectra were recorded using an excitation wavelength of 532 nm (Nd:YAG

laser) and most were taken using standard mode (with ×20 or x10

magnification). Raman spectra were acquired from 200 to 2000 cm-1 using a

power of 10 mW on the sample, with an acquisition time of 30 seconds (3

cycles) and about 2 cm-1 resolution. Rayleigh scattering was blocked by a

holographic notch filter, the backscattered light was dispersed on an 600

grooves/mm holographic grating and the slit was set at 100 μm. The

calibration of both Raman spectrometers was done using the main Raman

5

band of a diamond at 1332 cm-1. To confirm the results, in most cases,

measurements repeated on at least two different points.

Energy-dispersive X-ray fluorescence (EDXRF) analyses were carried

out, at GGL, with an ARL Quant'X from Thermo Scientific. Special set of

parameters was used, optimized for the most accurate analysis of jade

with various conditions for voltage (six steps from 5-30 kV) and lifetime

(200-300 seconds). Measurements' spot size was about 2 mm in diameter.

Absorption spectra for the 200-1600 nm range were recorded, at GGL, when

possible, using a Cary 5000 Ultra-Violet-Visible-Near Infrared (UV-Vis-

NIR) spectrometer. The data sampling interval (DI) and spectral bandwidth

(SBW) of each measurement were set at 0.7 nm and the scan rate at 60

nm/min. FTIR upolarized absorption spectra on all the transparent to

infrared samples carried out with a Varian 640 FTIR spectrometer at GGL;

from 6000 to 400 cm-1, using 4 cm-1 resolution and 64 scans (background

spectra were collected using the same parameters). A Bio-Rad Excalibur

spectrometer coupled with a Varian UMA500 FTIR microscope fitted with an

MCT detector cooled by liquid nitrogen was used for FTIR micro-

reflectance measurements, on all 16 samples, at SNM, from 4000 to 650

cm-1, using 4 cm-1 resolution and 64 scans (background spectra were

collected using the same parameters).

Results & Discussion

All samples of Table 1 were translucent, only the JDXX021 was

semitransparent, with homogenously distributed green color; under

microscope all presented similar features. Their specific gravity ranges

from 3.33 to 3.37 (for specific measurements see again Table 1). Samples

were inert under long- and short- wave UV excitation; only one (JDBU001)

presented faint green reaction under long-wave. These results are in

accordance to those previously published on omphacite- and jadeite- rich

samples.[1,8,20]

6

In Figure 1 Raman spectra of two samples (JDXX021 and JDXX051) from

200 to 1200 cm−1 are presented, as well as of two reference samples of

jadeite and omphacite minerals.[21] A shift of the main Raman band, due

symmetric stretching of the Si-O-Si bond, at JDXX021 is at around 695 cm−1

similar to those of jadeite and at JDXX051 at 680 cm−1 similar to those

of omphacite.[12,21-23] Moreover, the sample JDXX021 present two Raman bands

are 985 and 1035 cm−1 whereas JDXX051 a large band (probably a doublet)

centered at 1015 cm−1 (see again figure 6). Less intense bands are also

observed at the region bellow 650 cm−1. For the rest of gem quality

samples (see Table 1), the Raman spectra of JDRUS01 are similar to those

of omphacite and of the other four (JDBU001, JDRUS02_2, JDRUS02_3 and

JDXX002; see table 1) to those of jadeite.

Figure 1: Raman spectra from 200 to 1200 cm-1 of JDXX021 (jadeite-jade; bottom spectrum)and JDXX051 (omphacite-jade; upper spectrum). The second spectrum from the bottom is areference spectrum of jadeite (sample number R070117 from RRUFF database) [21] and thesecond from the top is a reference spectrum of omphacite (sample number R061129 from

RRUFF database). [21] All spectra are shifted vertically for clarity.

7

Figure 2: Raman spectra from 200 to 1200 cm-1 of PP15_1 (jadeite-jade; bottom spectrum)and PP10 (omphacite-jade; upper spectrum). The second spectrum from the bottom is areference spectrum of jadeite (sample number R070117 from RRUFF database) [21] and thesecond from the top is a reference spectrum of omphacite (sample number R061129 from

RRUFF database). [21] All spectra are shifted vertically for clarity.

In Figure 2 Raman spectra of samples PP10 and PP15_1 from 200 to 1200

cm−1 are presented, as well as of the two reference samples presented in

Figure 1.[21] Sample PP10 presents spectrum similar (with the main band at

678 cm-1) to those of omphacite and sample PP15_1 (with the main band at

690 cm-1) to those of jadeite. In Figure 3 Raman spectra of samples

A1750_5 and A47625 along with reference Raman spectra of jadeite and

omphacite presented in Figures 1 and 2. The main band of the sample

A1750_5 is at around 680 cm-1 and of the sample A47625 at around 695 cm-1.

Taking in account also their less intense Raman bands A1750_5 is an

omphacite-jade and A47625 a jadeite-jade. Raman spectra of the other five

samples of archaeological interest (A469_4, A810, A8831, A31392 and

A33853; see table 2) are also similar to those of omphacite.

8

Figure 3: Raman spectra from 200 to 1200 cm-1 of A47625 (jadeite-jade; bottom spectrum)and A1750_5 (omphacite-jade; upper spectrum). The second spectrum from the bottom is areference spectrum of jadeite (sample number R070117 from RRUFF database) [21] and the

second from the top is a reference spectrum of ompacite (sample number R061129 from RRUFFdatabase). [21] All spectra are shifted vertically for clarity.

EDXRF analyses of all measured samples as well as the number of

cations in the chemical formula (calculated for six oxygens) are

presented at Table 3. As the separation between Fe+2 and Fe+3 cannot be

done using EDXRF, total iron was measured as Fe+3 (or Fe2O3). Moreover, in

some samples small amounts of other elements were also detected (bellow

100 ppm); such as K, Ni, Cu, Sn, Zn, Ga, Sr, Zn . The measured pyroxenes

were classified following the Q-J pyroxenes diagrams, where Q=Ca+Mg+Fe+2

and J=2Na (see figure 4). [24] Sodic and sodic-calcic pyroxenes are plotted

in the region between the parallel lines Q+J=1.5 and Q+J=2.0; with

J/(Q+J)>0.8 for sodic (including jadeite), whereas with 0.2<J/(Q+J)<0.8

for sodic-calcic (including omphacite). In table 3 is observed that the

samples present Q+J values from 1.78 to 2.15; thus all samples were

indeed sodic and sodic-calcic pyroxenes. The Q+J values above 2 presented

in some of the samples are probably due to EDXRF drawback to measure

9

"light elements"; i.e., elements with atomic number bellow 12 (for

instance Na). Six of the samples presented J/(Q+J)>0.8 -with values from

0.84 to 0.94- consistent with sodic pyroxene; the samples JDRUS01,

JDXX051 and PP10 presented 0.2<J/(Q+J)<0.8 (0.62, 0.59 and 0.54

respectively) consistent with sodic-calcic pyroxene. Following Adamo et

al., 2006[8]; it should Al/(Al+Fe3+)>0.5 while the boundary between

jadeite and omphacite is set at Na/(Na+Ca)=0.8 (for jadeite it is higher

than 0.8, for omphacite between 0.2 and 0.8). In table 3, these ratios

were calculated and the results are in accordance to those used Morimoto

et al., 1988 [24] plot; i.e., JDRUS001, JDXX051 and PP10 samples are

omphacite jade and the other six jadeite jade. There results are in

agreement with Raman spectroscopy results.

JDBU001 JDRUS01 JDRUS02_2 JDRUS02_3 JDXX002 JDXX021 JDXX051 PP10 PP15_1

Na2O 14.29 9.17 13.11 12.95 13.33 13.32 9.28 7.86 11.11

MgO 1.57 7.65 3.22 2.42 1.58 1.36 9.84 8.36 1.73

Al2O3 22.52 12.33 19.45 20.65 21.09 21.23 12.53 13.44 16.34

SiO2 59.30 56.41 55.85 57.69 58.04 59.95 56.26 54.46 51.89

CaO 1.47 10.09 4.24 3.91 3.49 2.72 9.96 12.22 3.31

TiO2 0.19 0.30 0.30 0.26 - 0.10 0.05 - -

V2O3 - 0.07 0.17 - 0.05 0.02 0.08 0.04 -

MnO 0.02 0.09 0.04 0.03 0.03 0.02 0.04 0.13 0.30

Cr2O3 0.14 0.41 0.96 0.06 0.10 0.02 0.26 - -

Fe2O3 0.57 3.00 2.38 1.87 2.15 1.12 1.39 3.12 14.08

TOT 100.07 99.52 99.72 99.84 99.86 99.86 99.69 99.63 98.76

Na 0.94 0.63 0.88 0.86 0.89 0.88 0.63 0.54 0.78

Mg 0.08 0.40 0.17 0.12 0.08 0.07 0.52 0.44 0.09

Ca 0.05 0.38 0.16 0.14 0.13 0.10 0.37 0.46 0.13

Al 0.90 0.51 0.80 0.84 0.85 0.85 0.52 0.56 0.70

10

Fe 0.01 0.08 0.06 0.05 0.06 0.03 0.04 0.08 0.38

Q[10] 0.13 0.78 0.33 0.26 0.21 0.17 0.89 0.90 0.22

J[10] 1.88 1.26 1.76 1.72 1.78 1.76 1.26 1.08 1.56

Q+J[10] 2.01 2.04 2.09 1.98 1.99 1.93 2.15 1.98 1.78

J/(Q+J)[10] 0.94 0.62 0.84 0.87 0.89 0.91 0.59 0.54 0.88

Al/(Al+Fe)[8] 0.99 0.86 0.93 0.94 0.93 0.97 0.93 0.87 0.65

Na/(Na+Ca)[8] 0.95 0.62 0.85 0.86 0.87 0.90 0.63 0.54 0.86

Table 3:EDXRF analysie, calculation of Si, Na, Mg, Ca, Al and Fe atoms based on 6

oxygens and calculated values following Morimoto et al., 1988 [24] and Adamo et al., 2006[8]

Figure 4: Studied samples plotted in the diagram proposed by Morimoto et al. 1988.[24]

Six samples (JDBU001, JDRUS02_2, JDRUS02_3, JDXX002, JDXX021 and PP15_1) are in sodic

pyroxenes area (right bottom corner with 1.5<Q+J<2 and J/(Q+J)>0.8) where jadeite

pyroxene belongs and two samples (JDRUS001, JDXX051 and PP10) are in sodic calcic

pyroxenes area (middle of the graph: 1.5<Q+J<2 and 0.2<J/(Q+J)<0.8) where omphacite

pyroxene belongs. Some samples present Q+J>2 probably due to EDXRF drawback to measure

light elements (such as Na).

11

Figure 5: Unpolarized absorption spectra from 300 to 1000 nm of JDXX021 (jadeite-jade;bottom spectrum) and JDXX051 (omphacite-jade; upper spectrum). The spectra are normalized

to a milimeter thickness and the upper spectrum (JDXX051) is offset of 0.1 absorbanceunit for clarity.

In Figure 5, UV-Vis-NIR absorption (unpolarized) spectra from 300

to 1000 nm of samples JDXX021 and JDXX051 are shown, representing

jadeite- and omphacite-jade respectively. Two spectra present similar

absorptions, only their relative intensities vary. More precisely, the

large band at 380 nm, double sharp band at around 440 nm and the broad

bands at around 620 and 850 nm were attributed to Fe+3 absorptions.[25-27]

The bands centered at around 450 nm and 640 nm as well as the shoulder at

around 690 nm, are attributed to Cr+3.[26-28] Total absorption is observed in

the ultraviolet range bellow 330 nm in both samples. The large band

centered at 570 nm, attributed to intervalence Fe+2-Fe+3 charge transfer

as well as the absorptions in the above 900 nm attributed to Fe+2 are

relatively low (more intense at JDXX021 spectrum). [25,27] It looks also

that the main causes of natural color of both omphacite- and jadeite-

jade are Cr+3 and Fe+3. Similar absorption bands were obtained on the

12

other studied gem quality samples, only their relative intensities vary

(independently if it consists of omphacite- or jadeite- jade).

In Figure 6 the FTIR unpolarized absorption spectra from 4000 to

2600 cm−1 of the samples JDXX021 and JDRUS01are presented; total

absorption/or no bands are recorded below 2600 cm−1 and above 4000 cm−1.

Pyroxenes, in general, are considered nominally anhydrous minerals; i.e.,

can contain measurable amounts of hydrogen, sometimes observable from

3800 to 3000 cm−1 at the a.k.a. hydroxyl (OH) region.[29] Their hydroxyl

concentrations increase with pressure which they were formed. [30] Three

groups of hydroxyl related absorption bands are observed on the two

samples (as well as on the other gem quality samples measured) in the

regions around 3610, 3520 and 3450 cm−1; with several attributions found

in literature. [29-33] Their intensity differ from sample to sample

(independently if it consists of omphacite- or jadeite- jade). The groups

of bands observed at around 2950 cm-1 are not related with hydroxyl of

the samples but to organic matter; most likely due to C-H vibrations of

finger fat or due to wax residues used after polishing.[34] Sometimes, at

around 3000 cm-1 series of bands related to jade polymer treatment are

observed; [34] these bands were not observed on the studied samples.

13

Figure 6: Unpolarized FTIR absorption spectra from 4000 to 2600 cm-1 of JDXX021 (jadeite-

jade; bottom spectrum) and JDXX051 (omphacite-jade; upper spectrum). The spectra are

normalized to milimeter thickness and the upper spectrum is offset of 0.1 absorbance unit

for clarity.

14

Figure 7: FTIR micro-reflectance spectra from 1500 to 650 cm-1 of JDXX021 (jadeite-jade;

bottom spectrum), JDBU001 (jadeite-jade; second bottom spectrum), JDRUS01 (omphacite-

jade; third bottom spectrum) and JDXX051 (omphacite-jade; upper spectrum). All spectra

are offset of for clarity.

In figure 7 the FTIR reflectance spectra using a microscope from

1500 to 650 cm−1 of the samples JDXX021, JDBU001, JDRUS01 and JDXX051 are

presented. Total reflectance/or no bands are recorded above 1500 cm−1; in

some cases weak bands were observed. The bands in different publications

of reflectance spectra were described in different ways, sometimes with

reflectance bands and some other times after Kubelka-Munk transformation;

in this publication the reflectance bands are directly described. In

JDXX021 and JDBU001 (two bottom spectra) the main reflectance band is

situated at around 1080 cm-1 and in JDRUS01 and JDXX051 (two top spectra)

is situated at around 1070 cm-1. The exact position of the main band

depends mainly of the chemistry of the sample; it looks that in the most

omphacite jade are situated bellow 1075 cm-1 and the most jadeite jade

above 1080 cm-1.[4,5,35]. The positions of all the other reflectance bands

vary from sample to sample. The main band of the other three gem quality 15

samples (JDRUS02_2, JDRUS02_3 and JDXX002; see table 1) is above 1080 cm-

1; consistent with jadeite jade. This is in accordance with their

chemistry and Raman spectra (see again Figures 1 and 4 and Table 3).

However, it looks that omphacite- vs jadeite- jade separation is not

always clear solely based on reflectance FTIR spectra.

Figure 8: FTIR micro-reflectance spectra from 1500 to 650 cm-1 of PP15_1 (jadeite-

jade; bottom spectrum), A47625 (jadeite-jade; second bottom spectrum), PP10 (omphacite-

jade; third bottom spectrum) and A1750_5 (omphacite-jade; upper spectrum). All spectra

are offset of for clarity.

Four FTIR micro-reflectance spectra from 1500 to 650 cm−1 of the

samples PP10, PP15_1, A1750_5 and A47625are presented in figure 5. In

agreement with their chemisty and Raman spectra data (Figures 2 and 4 and

Table 3), the band of PP10 is at around 1060 cm-1 and of PP15_1 at around

1080 cm-1; consistent respectively with those of omphacite- and jadeite-

jade. The band of the sample A47625 is at around 1080 cm-1 and of A1750_5

at around 1060 cm-1; which is suggestive that consists of jadeite- and

omphacite- jade respectively. At FTIR micro-reflectance spectra of the

other five archeological samples (A469_4, A810, A8831, A31392 and A33853;16

see table 2) a band bellow 1075 cm-1 is present, which suggests that are

omphacite-jades.

Conclusion

Using Raman spectroscopy on seven gem quality samples, it was

confirmed that two of them are omphacite-jade and the other five jadeite-

jade. Additionally, it was found that rough sample PP15_1 collected from

sites exploited during Neolithic is jadeite-jade whereas PP10 is

omphacite-jade. Six axeheads excavated in different places in Switzerland

(A1750_5, A469_4, A810, A8831, A31392 and A33853) were found to be

omphacite-jades and one sample (A47625) jadeite-jade. EDXRF analysis on

nine samples (seven gem quality samples presented at Table 1 as well as

PP10 and PP15_1) confirm Raman spectroscopy results. Micro-FTIR spectra

in reflectance sixteen samples are also in accordance with the Raman

spectroscopy data. Analysis using UV-Vis-NIR and FTIR absorption

spectroscopy as well as classical gemological methods, on the seven gem

quality samples showed that omphacite- and jadeite- jade are similar;

thus cannot be used for their separation. These similarities strongly

suggests to include gem quality omphacitite in the jade family. It seems

that Raman spectroscopy is the most efficient method to identify if it

consits of omphacitite or jadeitite. Meanwhile, further studies are

needed on samples which contain both ompacite and jadeite minerals in

order to check their Raman, micro-FTIR in reflectance and EDXRF data in

order to see which method (or combination of methods) could be used to

proper identify them.

Acknowledgements

The authors are grateful to xxx Company, Hong Kong for the loan of the sample JDXX051

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