Post by gnopals on Oct 23, 2009 14:32:39 GMT
From gemologyproject.com/wiki/index.php?title=Opal
"The firms of Gilson in France and Chatham in the United States currently create synthetic opals. They are produced with white and black body colors. Chatham also markets a "crystal" type which exhibits a colorless body with play of color.
This laboratory created material was first marketed by Pierre Gilson, Sr. in 1974. It involves a 3 stage process involving the purification of chemicals involving fractional distillation. This is characteristically an elaborate process invoving consolidation of these refined chemicals under water pressure. The result is the creation of microscopic cristobolite silica spheres (SiO2) of uniform size. They are allowed to settle in the containment vessel for over a year in a hydrous solution of controlled pressure and acidity. Then, a hydrostatic press is utilized to consolidate the microspheres from a liquid phase into a solid phase, resulting in synthetic opal rough which can be cut into cabochons."
"The firms of Gilson in France and Chatham in the United States currently create synthetic opals. They are produced with white and black body colors. Chatham also markets a "crystal" type which exhibits a colorless body with play of color.
This laboratory created material was first marketed by Pierre Gilson, Sr. in 1974. It involves a 3 stage process involving the purification of chemicals involving fractional distillation. This is characteristically an elaborate process invoving consolidation of these refined chemicals under water pressure. The result is the creation of microscopic cristobolite silica spheres (SiO2) of uniform size. They are allowed to settle in the containment vessel for over a year in a hydrous solution of controlled pressure and acidity. Then, a hydrostatic press is utilized to consolidate the microspheres from a liquid phase into a solid phase, resulting in synthetic opal rough which can be cut into cabochons."
