Phot

os: S

hutte

rsto

ck (1

)

workshop & education skyray Instrument

The Fingerprint in GemstonesThe question of a gemstone’s provenance repeatedly arises in the trade because prices can vary drastically depending on a gem’s place of origin. Skyray Instrument has developed spectrometers that can analyse rare trace elements inside a stone without destroying or damaging the gem.

XRAY ANALYTICSXray Analytics Switzerland AG, Ltd.

Skyray Instrument Co. Ltd. AgentBrandisstrasse 59

8702 Zürich-Zollikon, Switzerland+41 (0)61 6817044

info@xray-analytics.comwww.xray-analytics.com

GEMSAquamarinAlexandrite

ApatiteBaryte Beryll

Chrysoberyll Danburite

DemantoidEmeraldGranate

Hematite Jade

NephriteOpal

PeridotQuartz

RhodochrositeRuby

SapphireSkapolite

SpessartineSpinel

Tanzanite Topaz

TsavoriteTourmaline

Zircone

METALSAluminumAntimonyCadmiumChromiumCobaltCopperGermaniumGoldIronIndiumIridiumLeadNickelNobiumManganeseMolybdenumOsmiumPalladiumPlatinumRhodiumRutheniumSilverTantaliumTinTitaniumVanadiumZinc

The Masterof ED-XRF Analysis

GEMSGEMSGEMSGEMS METALSMETALSMETALSMETALS

GOLDSCHMIEDEZEITUNG_77x302MM_FINAL.indd 1 04.02.16 13:25

Source: EDX-4500 I The Far East Gem Institute, Singapore

ED-XRF spectrum of a ruby from Kenya with detected trace elements thorium (Th), strontium (Sr) and zirconium (Zr). The strong rhodium signal (Rh) comes from the X-ray tube

VKa

CrKb

FeKb

GaKa

GaKb

ThLa

SrKa

ZrKa

ZrKb

RhKb

RhKa

ThLb

FeKa

CrKaV

Kb

ed-XrF spectrum

300

250

200

150

100

50

0

SrKb

high-tech made in china

What was still unthinkable a mere 15 years ago has now become reality and will form-atively shape the analysis of gemstones in future. First-class X-ray spectrometers are manufactured in the new technology area of Kunshan near Shanghai. Skyray Instru-ment, almost unknown ten years ago, is the biggest analytical manufacturer in China today. When the devices are config-ured for gemstone analysis, they deliver extraordinarily precise data. What had formerly been an analytical dream has suddenly become reality. The examiner is not only analyzing the main and minor elements, but also detects rare trace ele-ments coming from deep inside the gem-stone which are not detectable with other analytical methods and instruments.

These analytical devices grant access to an entirely new world for differentiating among rubies from Africa, India, Thailand or Burma. Renowned laboratories such as AIGS Thailand (Asian Institute of Gemmo-logical Sciences) use the “EDX-4500” and the “EDX-6000B” as daily working tools.

The new spectrometers from Skyray Instrument have confirmed the correctness of the analytical data which was first com-piled at the University of Singapore thirty years ago. Furthermore, elements now be-come visible which gemmologists had merely speculated about in the past. Zirco-nium (Zr) and niobium (Nb) are present in rubies from India. Rubies from Kenya are identifiable because they contain traces of strontium (Sr), yttrium (Y) and Thorium (Th), alongside high levels of zirconium (Zr). Numerous elements suddenly be-come visible in rubies from Africa, India, Thailand or Burma: these elements occur here as the most miniscule particles or inclusions that cannot be detected with a microscope.

Summary: The credibility of prove-nances stands and falls with the analysis of a stone that bears its “chemical fingerprint” inside itself. This “fingerprint” must now be redefined because high-performance, user-friendly and affordably priced analytic de-vices have become available for the first time. Andreas Burkhardt, Xray Analytics Switzerland; Willem B. Stern, University of Basel; Tay Thye Sun, Far East Gem Institute, Singapore www.xray-analytics.com

The Chinese engineers Wang Jia Yong and Wu Min calibrate the new ED-XRF-spectrometer for

gemmological analyses together with Dr. Andreas Burkhardt (right)

CPS

IIs this ruby from Burma or Madagascar? Was this deep-blue sapphire mined in Kashmir or China? Drastic price differences impel all re-nowned laboratories to devote special attention to the difficult question of determining the provenance of gemstones. Reliable analyses are all the more essential and decisive when a stone is already set or when it’s offered for sale without specification of its provenance.

detection oF trace elements

Thorough mineralogical and gemmological examination of the stone is the precondition for a reliable determination of its provenance. Sixty rubies from Burma and Thailand were examined with PIXE (Proton Induced X-ray Emission) at the University of Singapore for the first time thirty years ago. Soft protons are fired at the rubies in this complicated and cost-ly method, which is feasible only in a universi-ty’s laboratory. Trace elements such as titani-um, vanadium, chrome, iron and gallium, as well as silicon, chromium, potassium and cal-cium, were detected in these Burmese and Thai rubies for the first time. These findings were only partially acknowledged or even called intodoubt when they were initially published.

Energy-Dispersive X-ray Fluorescence spectrometers, performing the ED-XRF meth-od by analyzing the atoms with electrons, were first designed in the 1980th. The ED-XRF is ab-solutely non-destructive and all elements form sodium to Uranium are simultaneously dis-played in the spectrum on the monitor. Con-sidering the abundance of natural stones and new mining discoveries the question arises: Are determinations of provenances still possi-ble and confirmed by chemical analysis? If so, there must yield a significant “chemical finger-print”. Only this can serve as the basis for reli-able and credible reports of gemmological ex-aminations.

196 GZ 03/16

Source: Prof. Dr. Willem B. Stern

Rubies from Africa (A), Mogok in Burma (M), India (I) and Thailand (T) form significant groups when the elements aluminium (Al), gallium (Ga), chrome (Cr) and vanadium (V) are depicted via statistical programmes

results of the ed-XrF analysis

Cr / V

1e+5

1e+41e+0 1e+1 1e+2

Al /

Ga

Ruby ED-XRF

1e+3 1e+4 1e+5

M M

M

M MM

M

MM

MMMA A

A

AAAA A AAA

A A

T TT

TTTTT

T

TI II

II I III

AAA