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Beryllium diffusion vs heat treatment in yellow corundum: NGJA Raman spectral markers?

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M
Marta Stones•910 rep

What laboratory spectrometry methods distinguish lattice-diffused yellow sapphires treated with beryllium oxide from unheated natural golden corundum?

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5 Answers from travellers

✓Accepted Answer

Beryllium diffusion involves baking light or colorless corundum in crucibles packed with BeO powder at temperatures exceeding 1750°C. Because beryllium has a very small ionic radius, it diffuses deeply into the crystal lattice, trapping color centers that produce a vivid golden-yellow or padparadscha hue. It cannot be detected by standard refractometers or standard loupes. The NGJA laboratory uses Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) or Secondary Ion Mass Spectrometry (SIMS) to detect light-element Be concentrations down to parts-per-million (ppm) levels, distinguishing it from natural iron-trapped color.

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D
Dr Kularatne•1950 rep

Immersion microscopy in methylene iodide frequently reveals an artificial color rim that follows the faceted perimeter if the stone was re-cut after diffusion.

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M
Marta Stones•910 rep

Untreated natural yellow sapphires regularly display sharp 450nm iron absorption lines under a desk spectroscope, whereas diffused stones show anomalous synthetic spectra.

18
E
Elena Granite•925 rep

Natural rutile silk inclusions melt into circular discoid tension halos at the extreme temperatures required for beryllium lattice diffusion.

15
D
Dr Senaka Soil•1820 rep

Always demand a memo certificate issued directly by the National Gem and Jewellery Authority before wiring export funds for large yellow parcels.

13
I
Ian Flavors•880 rep

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