GEMSTONE ANALYSIS continued


After a 0.1-sec scan, the GemScan 1350 Raman spectrometer and data comparison software (AcuTech Scientific, Inc., San Diego, CA) can identify a gemstone or mineral for spectral fingerprinting. Raman spectral finger- prints for the chemical components of jade components SiO2 Fe2


, Al2 O3 cm-1


, MgO, CaO, and Na2 and 1100 cm-1


O3 , Cr2 O3 ,


O have signature Raman spectra between 300 . A comparison of type A jade, resin-filled type B jade,


and quartz is shown in Figure 2. Distinctive Raman spectral differences between diamond, moissanite, and quartz are shown in Figure 3, and spectral differences between natural red coral and dyed coral are shown in Figure 4. The red trace in Figure 4 represents the presence of carotenoids and parrodines; these two natural color pigments are missing in the dyed corals (blue trace).


Fast Raman spectral identification


The GemScan1350 Raman molecular spectral identification and data- handling system characterizes gemstones in less than 2 seconds. It comprises x-y-z lead screws and a turntable for 3-D control and laser scanning. A laser scans and identifies the Raman spectral fingerprint of a loose small diamond as well as large gemstones up to 5 cm high × 10 cm diameter in 360° of the surface. Figure 5 highlights the differ- ence between diamond and diamond simulant on the market. The Raman shift for this diamond simulant has a broader Raman spectrum with six major Raman shifts. The VVS1-F grade diamond has a single


Figure 5 – Comparison of Raman spectrum of a VVS1-F grade diamond (black spectrum) to a diamond simulant (red spectrum). Data obtained from GemScan1350. (© Copyright AcuTech Scientific, Inc. All rights reserved. Image reproduced with permission of AcuTech Scientific, Inc.)


Laboratory Furnaces • +RUL]RQWDO


6LQJOH DQG 0XOWL =RQH


• %R[ )XUQDFHV • 7HPSHUDWXUHV XS WR • 0DGH LQ WKH 8 6 $


• $YDLODEOH ZLWKLQ 7ZR :HHNV


°&


6PDUW&RQWURO 7RXFK 6FUHHQ &RQWURO 6\VWHP


9HUWLFDO 7XEH )XUQDFHV


Figure 6 – Raman spectra comparison for diamond (black spectrum) and counterfeit (red spectrum). Data obtained from GemScan1350. (© Copyright AcuTech Scientific, Inc. All rights reserved. Image reproduced with permission of AcuTech Scientific, Inc.)


carbon-carbon Raman shift at 1332 cm-1 . Figure 6 highlights the differ-


ence between diamond and counterfeit. Note the counterfeit has been identified as quartz at a 520 cm-1


Raman spectrum wavenumber. ZZZ WKHUPFUDIWLQF FRP • LQIR#WKHUPFUDIWLQF FRP AMERICAN LABORATORY 34


The authors are with AcuTech Scientific, Inc., 325 W. Washington St., San Diego, CA 92103, U.S.A.; tel.: 408-868-7707; e-mail: frankyang@acutechscientific.com; www.acutechscientific.com


JUNE/JULY 2017


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56