Recently the IGI Lab in Shanghai received an antique Etruscan revival style necklace from the mid to late 19th century, pictured above.
When the necklace was submitted, IGI gemologists immediately understood the reason it was sent for identification: It seemed to weigh less than it should and, therefore, was suspected to be made of gilt copper, rather than gold.
The Game’s Afoot
The equipment IGI Laboratories uses to detect precious metals employs EDXRF (Energy Dispersive X-Ray Fluorescence Spectrometry). This process can detect chemical elements with atomic number 12 or higher and analyze the content. In other words, under EDXRF detection, if the Au (gold) content shows 75%, then it means that the metal at the detection location is 18 karat gold.
In order to fully judge the material composition of this necklace, IGI gemologists selected three locations for testing, namely the surface of a pendant, a location where the internal metal is exposed, and a third, randomly selected testing area (all done with the customer’s consent).
Gemologists randomly selected one pendant on the necklace and tested it on the back.
The results showed that the composition of Au was 84.45%, and the purity was over 18K.
Of course the first test point is only an elemental surface analysis of the necklace. If the gold plated layer on the surface is not peeled or damaged, the result could still be 18K gold. This is the reason for step 2, testing chemical composition deep inside.
After examining the entire necklace, the laboratory selected a small cut on the back of the pendant directly beneath the necklace for dot measurement.
The results showed that the Au content was 60.27%, and the purity exceeded 14K.
Again, with the customer’s consent, gemologists randomly selected a location on the back of the necklace, scratched it with a blade, and scraped off the surface metal layer to form a 2 millimeter x 2 millimeter scratched area, exposing the internal metal for testing.
The results showed that the Au composition was 70.23%, with a purity of more than 14K and less than 18K.
According to these test results, this antique necklace in the Etruscan Revival style can be said to be made of “real gold,” despite some variances. This is due to the technological level of that era – the purity of gold produced then was not consistent – ranging from 14K to 20K gold.
Antique jewelry still has a certain status in today’s jewelry market, and it has greater collection value because of the history and stories behind it. In the long history of jewelry development, there were some deceptive practices. Some merchants sold jewelry with precious metal imitations and gemstone simulants. For example, during the Renaissance there was a flood of imitation pearls in the jewelry market in Venice. In 1502 The Venetians formulated special laws and regulations to preserve the city’s fine trading reputation, proclaiming that “Anyone who makes fake pearls will have their right hand chopped off and exiled for ten years.
It can be seen that the making of antique jewelry, like modern jewelry, placed great reliance on integrity and credibility. Finding shoddy examples is unusual and not the norm in the industry.