2023

Jadeite: impregnated and dyed

First published in Facette 28 (May 2023)

Figure 1: Treated jadeite-jade (polymer impregnated and dyed). Photo: L. Phan, SSEF.

Jadeite-jade of saturated emerald green colour is highly valued in Asia. It is therefore not astonishing to see in the market either heavily treated jadeite-jade or even imitations made of different minerals which pretend to be fine quality jadeite-jade of “Imperial green” colour.

An exemplary case was submitted last year, being a ring of 25 mm diameter and showing a vivid green colour as is known in chromium- bearing jadeite. A closer look however revealed distinct colour concentrations in fissures and along grain boundaries which made this quite a dubious item from the start (Figure 1).

The analyses at SSEF confirmed that this ring is a heavily treated jadeite of rather poor quality (many fissures). The jadeite had been first bleached with acids and subsequently impregnated with artificial resin (polymer) and additionally dyed artificially to create the green colour. Chemical analyses showed a rather pure jadeite composition with minor amounts of iron (0.7 wt% Fe2O3) but nearly no chromium (only 0.003 wt% Cr2O3). The absorption spectrum is distinctly different to chromium-bearing jadeite. It is dominated by three broad bands at about 430, 600 and 675 nm mainly resulting from the green dye, with additionally a small peak at 435 nm from Fe3+ (Figure 2).

Figure 2: Comparison of absorption spectra of the described jadeite artificially coloured by a green dye (red trace) and an untreated green jadeite coloured by traces of chromium (green trace). Figure: M.S. Krzemnicki, SSEF.
In addition, the infrared spectrum shows evident peaks related to artificial resin in the range from 2800-3100 cm-1 wavenumbers (Figure 3). In the Asian market, such a polymer impregnated and dyed jadeite -jade is called type B+C jadeite-jade and is of nearly no commercial value compared to an untreated jadeite-jade of similar colour.
Figure 3: Comparison of FTIR spectra of the described polymer impregnated and dyed jadeite (red trace) and an untreated green jadeite (green trace). Figure: M.S. Krzemnicki, SSEF.