Artificial Emeralds Cultivated by W. Zerfass: Chronicle, Growth Method, and Characteristics
In the 1960s, German scientist W. Zerfass made significant strides in the field of synthetic gemstones, particularly emeralds. His groundbreaking work in synthetic emerald growth has been extensively documented in gemological literature.
Zerfass's synthetic emeralds were produced using advanced crystal growth techniques, although the specific methods he employed are not fully disclosed. These techniques are believed to be related to flux growth and hydrothermal growth, methods that replicate natural emerald crystal formation in controlled high-temperature and high-pressure environments.
During the 1950s and 1960s, Zerfass's experiments in crystal growth took place, culminating in the presentation of the first faceted synthetic emeralds to the public in 1963. His work was part of a series of significant synthetic emerald advancements, which were discussed in gemological journals and reports around 2017 and 2018.
The synthetic emeralds grown by Zerfass exhibit properties typical of synthetic emeralds produced by flux or hydrothermal methods. They are known for their high clarity, particular inclusion types, and specific growth patterns visible under magnification. These properties help gemologists differentiate Zerfass’s synthetic stones from natural emeralds.
Research on Zerfass's synthetic emeralds focused on their growth-related properties, inclusions, and structural features that distinguish them from natural emeralds and other synthetic types. The aim was to characterise growth conditions, identify inclusions characteristic of the synthetic process, and explore physical and optical properties that affect quality and value.
Later experiments conducted by Zerfass and Jaeger aimed to reduce the concentration of trapped flux particles and obtain larger and cleaner material. Production of synthetic emeralds continued on a small scale during the 1960s and early 1970s, before terminating in 1973.
Two types of synthetic emeralds are produced: flux-grown and hydrothermal. While Nacken and Zerfass used only Cr-bearing compounds as color-causing trace elements, IG Farben added nickel carbonate to the melt for a slightly yellowish green color. Synthetic emeralds can be distinguished from natural ones by trace element analysis.
Synthetic emeralds often display inclusions that are visual evidence of their artificial growth. Crystal growth in the Zerfass process mainly occurred in a direction parallel to the c-axis. Emerald, a mineral beryl that contains beryllium and is colored by chromium and vanadium, is found in nature with various crystal habits, including the prismatic forms observed in Zerfass's synthetic emeralds.
The larger Zerfass crystal had a short prismatic to thick tabular habit consisting of a 12-sided prism and two basal faces, while the smaller Zerfass crystal had a short prismatic form, with six dominant prism faces and one basal pinacoid.
Hydrothermal synthetic emeralds have a density of 2.67 - 2.71, refractive index of > 1.570, and birefringence of approx. 0.005-0.007. Flux-grown synthetic emeralds, on the other hand, have a density of 2.65 - 2.67, refractive index of 1.570, and birefringence of approx. 0.003-0.005.
In conclusion, while the precise proprietary details of W. Zerfass’s growth technology are not fully detailed publicly, his synthetic emeralds are associated with advanced flux or hydrothermal growth processes that produce high-quality synthetic emeralds with distinct gemological properties. These emeralds were characterised in the literature around 2017-2018, with focus on their growth technology and distinguishing features compared to natural stones.
[1] Reference: [Gemological Institute of America (GIA), 2018]
- In the realm of gemmology, ongoing research and discussions about W. Zerfass's synthetic emeralds focus on their growth-related properties, inclusions, and distinguishing features, particularly in comparison to natural emeralds and other synthetic types. (science, gemmology, synthetic emeralds, research)
- Since the 1960s, gemstone enthusiasts and professionals have taken advantage of Zerfass's breakthroughs in the field by attending workshops and courses that delve into the intricacies of his synthetic emerald growth methods. (workshops, courses, Zerfass's synthetic emeralds)
- As the field of gemmology advances, continued research on synthetic emeralds like those produced by Zerfass serves a practical purpose, helping gemologists address the unique medical-conditions and technological challenges associated with the distinction and appraisal of synthetic versus natural gemstones. (medical-conditions, technology, synthetic gemstones)
