Slocum Stone
Slocum Stone is classified as an opal imitation material according to the provisions of the CIBJO (The Gemstone Book) . Named after the inventor "John Slocum", this imitation is a sodium-calcium-magnesium- silicate glass , which shows an optical behavior similar to the play of colors of precious opals.
Slocum-Stone was produced in five basic colors - "White", "Crystal", "Amber", "Semi-Black" and "Black" and was first marketed in 1976 by MDI Corporation (Michigan / USA).
In addition to the properties typical of glass, such as gas bubbles and streaks, the most striking distinguishing feature is the clear directional dependence of the play of colors-like effect. While the "play of colors" can be clearly seen from above, this impression is much less pronounced when viewed from the side.
The clear cause of the optical effect was determined to be interference phenomena on tinsel-like, wafer-thin (0.3 micrometers) flakes of different sizes made of aluminum foil.
Details of the process used to manufacture the opal imitations were not known and are not patented.
Production was stopped after the inventor's death, but there are patented methods of making similar materials.
Individual evidence
- ↑ Crowningshield, R. (1976): The Slocum imitation opal put on the market, Gems & Gemology, Vol. 15, No. 6, p. 185
- ^ Dunn, PJ (1977): Observations on the Slocum Stone, Gems & Gemology, Vol. 15, No. 9, p. 252.
- ↑ O'Donoghue, M. (2006): Gems: their sources, descriptions and identification (sixth edition). Oxford, United Kingdom: Butterworth-Heinemann. p. 548. ISBN 978-0-7506-5856-0
- ↑ Burch, CR (1985): A re-examination of Slocum Stone-with particular emphasis on inclusions, Journal of Gemmology, Vol. 19, No. 7, pp. 586-596.
- ↑ Gemstone material, United States Patent 7290404