Gemstone Grading and Purity Control with WDS

Cubic zirconia (ZrO2) is a popular synthetic gemstone used as an economic substitute for diamonds in jewelry (Fig. 1). Calcium oxide (5–8 wt.%) or yttrium oxide (15–18 wt.%) are often added to stabilize the ZrO2 crystals. Moreover, other elements such as hafnium may also be present in minor amounts.

The EDS spectrum of a cubic zirconia (Fig. 2) shows a broadened, irregular Zr L peak but the contribution of other elemental lines cannot be distinguished easily. The WDS spectrum, in contrast, clearly resolves the various Zr L energy lines from the Y L energy lines and even detects Hf using M series energy lines. QUANTAX WDS with its high spectral resolution capability can thus be a valuable tool for gem grading and purity control.

Fig. 1: Exemplary photo of jewelry with a synthetic gemstone made of cubic zirconia
Fig. 2: X-ray spectrum section for cubic zirconia in the energy region of 1.5 - 2.4 keV showing the high spectral resolution of WDS in comparison to EDS