Slocum stone (sometimes sold as "Slocum opal") is an early

opal Opal is a hydrated amorphous form of silicon dioxide, silica (SiO2·''n''H2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a ...

simulant which was briefly popular prior to the introduction of synthetics and less expensive simulants. It was named after its inventor, John L. Slocum (1920–1998) of

Rochester, Michigan Rochester is a city in Oakland County, Michigan, Oakland County in the U.S. state of Michigan. The population was 12,711 at the 2010 United States Census, 2010 census. It is a northern suburb in Metro Detroit located 20 miles north of the city of ...

. John Slocum experimented during the 1960s with various methods. In 1971, he began marketing his first commercial simulant under the "Opal Essence" trade name. Not satisfied, he continued experimenting and in 1974 brought out the more realistic "Slocum Stone" type. However, Gilson synthetic opals and other imitation opals such as " Opalite" came onto the market soon thereafter and greatly diluted the market for "Slocum Stone" By 1976, this product was being manufactured by MDI Corporation. Slocum Stone is a

silicate glass Glass is an amorphous ( non-crystalline) solid. Because it is often transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window panes, tableware, and optics. Some common objects made o ...

which shows traces of

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

and

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

. It was manufactured in several base colors, and the

opalescence Opalescence or play of color is an optical phenomenon associated with the mineraloid gemstone opal,opalescent. 2019. In Noah Webster's 1828 American Dictionary of the English Language. Retrieved January 7, 2019, from https://1828.mshaffer.com/ ...

is produced by very thin layers of metallic film (estimated at 30 nanometres in thickness), in the form of translucent flakes, which produce a

thin-film interference Thin-film interference is a natural phenomenon in which light waves reflected by the upper and lower boundaries of a thin film Interference (wave propagation), interfere with one another, increasing reflection at some wavelengths and decreasing it ...

effect. These flakes themselves lend color, along with colorant within the glass base. Bubbles and swirls typical of glass are other typical inclusions which may be noticed under magnification. In later examples, built-up laminations are visible when viewed from the side.Gem Gallery: Opal, Slocum Stone photographs
" theimage.com

from the original on 12 November 2009. Retrieved 12 November 2009.

References

{{Reflist Synthetic minerals Products introduced in 1974 Opals Nanomaterials Thin-film optics