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The touchstone was used during the Harappa period of the Indus Valley civilization ca. 2600–1900 BC for testing the purity of soft metals. [2] It was also used in Ancient Greece. [3] The touchstone allowed anyone to easily and quickly determine the purity of a metal sample.
Apart from X-ray spectrometer technique, other older traditional methods are using the TouchStone and Acid to test the gold purity. But TouchStone and Acid are destructive testing - a tiny sample of gold is cut and then tested. The sample is rubbed on TouchStone and a drop of acid is put on it and the goldsmith observes the residue using a ...
In the past the assay was conducted by using the touchstone method but currently (most often) it is done using X-ray Fluorescence (XRF). XRF is used because this method is more exacting than the touchstone test. The most exact method of assay is known as fire assay or cupellation. This method is better suited for the assay of bullion and gold ...
1916 photograph of an assayer performing an electrolysis test on a gold sample at the United States Assay Office in New York. Fusion: the process requires a self-generating reducing atmosphere, and so the crushed ore sample is mixed with fluxes and a carbon source (e.g. coal dust, ground charcoal, flour, etc.) mixed with powdered lead oxide ...
The BIS system of hallmarking of gold jewellery began in April 2000. The standard specifications governing this system are IS 1417 (grades of gold and gold alloys, jewellery/artefacts), IS 1418 (assaying of gold in gold bullion, gold alloys and gold jewellery/artefacts), IS 2790 (guidelines for manufacture of 14, 18 and 22 carat gold alloys only ), IS 3095 (gold solders for use in manufacture ...
It is an extension of the older karat system of denoting the purity of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24) pure gold by mass. The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark , and the fineness may vary slightly from the traditional ...
The core services offered by SGS include: the inspection and verification of the quantity, weight and quality of traded goods; the testing of product quality and performance against various health, safety and regulatory standards; and the ascertainment of the conformance of products, systems or services with the requirements of standards set by ...
Kundan Group was established in 1971 and is headquartered in New Delhi, India.The company has a multi-business portfolio inclusive of gold refinery, cosmetics, chemicals, polymers, agro-commodities, precious metals, petroleum products, energy, and the import of bullion and pharmaceutical items.