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Rhenium–osmium dating is a form of radiometric dating based on the beta decay of the isotope 187 Re to 187 Os.This normally occurs with a half-life of 41.6 × 10 9 y, [1] but studies using fully ionised 187 Re atoms have found that this can decrease to only 33 y. [2]
By contrast, depletion gilding is a subtractive process whereby material is removed to increase the purity of gold that is already present on an object's surface. In depletion gilding, other metals are etched away from the surface of an object composed of a gold alloy by the use of acids or salts, often in combination with heat.
Gold is currently considered the heaviest monoisotopic element. Bismuth formerly held that distinction until alpha-decay of the 209 Bi isotope was observed. All isotopes of gold are either radioactive or, in the case of 197 Au, observationally stable, meaning that 197 Au is predicted to be radioactive but no actual decay has been observed. [4]
In 1970, South Africa produced 995 tonnes or 32 million ounces of gold, two-thirds of the world's production of 47.5 million ounces. [2] Production figures are for primary mine production. In the US, for example, for the year 2011, secondary sources (new and old scrap) exceeded primary production. [3]
Silver-gilt or gilded/gilt silver, sometimes known in American English by the French term vermeil, is silver (either pure or sterling) which has been gilded.Most large objects made in goldsmithing that appear to be gold are actually silver-gilt; for example, most sporting trophies (including medals such as the gold medals awarded in all Olympic Games after 1912) [1] and many crown jewels are ...
An 836-pound “cursed” emerald worth nearly $1 billion will be returned to Brazil after 15 years under lock and key in Los Angeles. The 180,000-carat Bahia Emerald was smuggled out of the South ...
(Reuters) -World leaders and U.S. politicians reacted to news that former U.S. President Jimmy Carter, who as president brokered peace between Israel and Egypt and later received the Nobel Peace ...
Bright gold or liquid gold is a solution of gold sulphoresinate together with other metal resinates and a bismuth-based flux. It is particularly bright when drawn from the decorating kiln and so needs little further processing. This form of gilding was invented or at least improved by Heinrich Roessler.