Black pearl
Description
A rare, pearl with an iridescent black color produced by black lipped oysters. Natural black pearls were indigenous to waters near Peru, Panama, and islands in Polynesia, Indonesia and the Phillipines. By 1900, overharvesting resulted in the near elimination of oysters that produced the black pearls. Because of their value, black pearls are often simulated by artificial methods. Prior to the 1970s, most commercial black pearls were dyed by soaking in a weak solution of nitrate silver nitrate and dilute hydroxide ammonia. The black color was then developed by exposure to light or sulfide hydrogen sulfide gas. Another method used gamma radiation to change the color of Akoya pearls from white to black. Since 1966, techniques were developed for culturing black pearls at fairly rapid rates (2 mm per year).
Synonyms and Related Terms
black pearls; gray pearls; grey pearls; Tahitian pearls. Polynesian pearls; zwarte parel (Ned.)
Other Properties
Natural and cultured black pearls: fluoresce reddish brown in long UV light
Dyed black pearls and irradiated do not fluoresce.
Hazards and Safety
Easily damaged by acids. Deteriorates at low humidities. Easily scratched. May be discolored by soap or skin oil.
Additional Information
Pearl: Website
Authority
- Website address 1, Website address 1 Comment: http://www.geo.utexas.edu/courses/347k/redesign/gem_notes/pearl/pearl_main.htm
- Website address 2 Comment: http://www.perlesdetahiti.net/index.php?key=2