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2. Touchstone (assaying tool) - Wikipedia

   en.wikipedia.org/wiki/Touchstone_(assaying_tool)

   This method has been used since ancient times. In modern times, additional tests can be done. The trace will react in different ways to specific concentrations of nitric acid or aqua regia, thereby identifying the quality of the gold: 24 karat gold is not affected but 14 karat gold will show chemical activity.

3. Metallurgical assay - Wikipedia

   en.wikipedia.org/wiki/Metallurgical_assay

   A model of a late 19th-century Canadian seal used to certify the quality of assayed gold. A metallurgical assay is a compositional analysis of an ore, metal, or alloy, usually performed in order to test for purity or quality. Some assay methods are suitable for raw materials; others are more appropriate for finished goods.

4. Karatmeter - Wikipedia

   en.wikipedia.org/wiki/Karatmeter

   Due to its very high precision and fast result, X-ray analysis has been adopted by international agencies in India as part of the certification process used to hallmark gold. [1] It is an accurate, non-destructive means of testing the purity of gold and other related elements. Analyzing gold using XRF spectrometers gives the purity of gold, up ...

5. Assay office - Wikipedia

   en.wikipedia.org/wiki/Assay_office

   Assay offices are institutions set up to assay (test the purity of) precious metals. This is often done to protect consumers from buying fake items. Upon successful completion of an assay (i.e. if the metallurgical content is found be equal or better than that claimed by the maker and it otherwise conforms to the prevailing law) the assay offices typically stamp a hallmark on the item to ...

6. Acid test - Wikipedia

   en.wikipedia.org/wiki/Acid_test

   An acid test is a qualitative chemical or metallurgical assay utilizing acid. Historically, it often involved the use of a robust acid to distinguish gold from base metals . Figuratively, the term represents any definitive test for attributes, such as gauging a person's character or evaluating a product's performance.

7. Oddy test - Wikipedia

   en.wikipedia.org/wiki/Oddy_test

   The Oddy test has gone through many changes and refinements over time. Whereas Andrew Oddy proposed to place each metal coupon in a separate glass container with the material to be tested, Bamberger et al. [4] proposed a "three-in-one" test, where all three metal coupons shared one container, simplifying the procedure.

8. Colored gold - Wikipedia

   en.wikipedia.org/wiki/Colored_gold

   White gold is an alloy of gold and at least one white metal (usually nickel, silver, platinum or palladium). [5] Like yellow gold, the purity of white gold is given in karats. White gold's properties vary depending on the metals used and their proportions. A common white gold formulation consists of 90% wt. gold and 10% wt. nickel. [4]

9. Wohlwill process - Wikipedia

   en.wikipedia.org/wiki/Wohlwill_process

   The resulting gold is 99.999% pure, and of higher purity than gold produced by the other common refining method, the Miller process, which produces gold of 99.5% purity. [1] [2] [3] For industrial gold production the Wohlwill process is necessary for highest purity gold applications.