Editing Touchstone (assaying tool) (section)

==History==
The touchstone was used during the [[Indus Valley civilization#Chronology|Harappa period of the Indus Valley civilization]] ca. 2600–1900 BC for testing the purity of soft metals.<ref>{{Cite book|title=Gold: A Cultural Encyclopedia|last=Venable|first=Shannon L.|publisher=ABC-CLIO, LLC|year=2011|isbn=978-0313-384318|location=Santa Barbara, CA|pages=264}}</ref> It was also used in [[Ancient Greece]].<ref>{{Cite book |last=Bisht |first=R. S. |year=1982 |chapter=Excavations at Banawali: 1974–77 |editor-last=Possehl |editor-first=Gregory L. |title=Harappan Civilization: A Contemporary Perspective |location=New Delhi |publisher=Oxford and IBH Publishing Co. |pages=113–124}}</ref>

The touchstone allowed anyone to easily and quickly determine the purity of a metal sample. This, in turn, led to the widespread adoption of gold as a standard of exchange. Although mixing gold with less expensive materials was common in coinage, using a touchstone one could easily determine the quantity of gold in the coin, and thereby calculate its intrinsic worth.