English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

07986 Gemological Institute of America T he first useful method of comparing the densities of substances as an aid to identification is attributed by Vitruvius (ca. 13 B.C.) to Archimedes, the famous Greek scientist (ca. 287-212 B.C.). As the story goes, Archimedes was asked by King Hieron I1 of Syracuse to determine if a newly delivered crown was pure gold as claimed by its maker. Archimedes received the inspiration for his now-famous displacement method of determining comparative densities when he stepped into a brimming bathtub and noted the overflow caused by the added volume of his body. Inspiration struck-Eureka! -the water displaced must be equal to the volume of any material inserted into it, and hence it must follow that for substances of equal weight, a "lighter" or less dense substance would displace more water than a "heavier" or denser material. A comparative volumetric displacement test of the crown and a mass of pure gold equal to i t in weight showed that the crown displaced more water, hence it had to be "lighter," hence i t had to be adulterated. This fundamental principle first enunciated by Archimedes is basically the one that we still follow in all measurements of specific gravity involving immersions in fluid. Incidentally; the scoundrelly goldsmith was executed. Although little progress was made in the hydrostatic measurement of specific gravity during more than 10 centuries following Archimedes's discovery, the increased interest in gemstones from the late 17th century on led to fairly rapid developments both of the method and of specific values from that time. Today, the hydrostatic technique for measuring specific gravity is a standard test in gemstone identification (see box). The following discussion traces the origins and development of this very basic gemological tool.

Contributions to A History of Gemology: Specific Gravity — Origins and Development of the Hydrostatic Method