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Essential Fire Assay Terms

22-Nov-11

TContext11_Hallm_Mic.doc

as used in Bibliography

"Hallmark (-ing)"

Author

Context

IAAO

Hallmarks are marks applied to precious metals to indicate the amount of pure metal in the alloy. Traditionally applied by striking with a punch, hallmarks can now also be applied using lasers.

IAAO

... hallmarking is carried out by assay offices which are situated in many countries over the world, but are most prevalent in Europe, the Middle-East and Asia. In some countries, assay offices are operated by the state and in others they are run as private operations. Some countries operate compulsory systems, others operate voluntary systems. The vast majority, but not all offices, are independent of the customers they serve.

For a detailed summary of National gold jewellery caratages and marking requirements please click here (pdf 183 KBytes)

"Microcupellation"  or  "Micro-Cupellation"

Author

Context

Corti

Sample size is typically about 250 mg, although microcupellation techniques allow for much smaller samples of about 10 mg with consequent shorter processing time.

At such small sample sizes, ensuring that it is representative of the bulk alloy becomes more difficult.

Brill

Microcupellation has become established in recent years, within the context of the cupellation of gold according to ISO 11426; with only about 10 mg of material taken from concealed places of a jewellery article by scraping, microcupellation can be carried out in a short time as clearly described in Table 11. (see Table 11 within full article: "Analysis of Carat Gold", GT, nº 22, Jul. 1997).

...very accurate gold fineness (determinations) are obtained by microcupellation. Of course, a microbalance is essential for the weighing procedure; otherwise the usual equipment specified in ISO Standard 11426 can be employed,

 

 

Micro-Cupellation and its Implementation     Method of the Irish Assay Office:

 

  Proposal ISO 11426 amended for small test portions              As for  ISO 11426 but with the following amendments:

Brill

● Test portion 9 mg to 10.5 mg, weighed to ± 0.001 mg

● It is optional to anneal beads after flattening them on anvil

● For samples containing approx. 999% gold, add 0.8 mg of copper to test portions of c.10 mg

● It is optional to roll them but, if omitted, aim to achieve strip thickness of 0.12 mm to 0.15 mm by hammering and follow by annealing.

● Lead foil 2 g

● Omit rolling strips into cornets if too small to do so

● Furnace temperature approx. 1065º C.

● Duration of samples in acid bath (density 1.2 g/cm3 ) in minutes

● Duration in furnace 8.5 to 9 minutes.

● Duration of samples in acid bath (density 1.3 g/cm3 ) in minutes

● Omit brushing precious metal buttons

● Where Pt basket used, place the basket with the gold samples contained in silica thimbles for about 2 - 3 min. in a muffle furnace heated to ~900°C

 

 

English

Deutsch

Nederlans

Français

Italiano

Castellano

Русский

 

 

 

 

 

 

 

cupellation /
micro(
~)

Kupellation /
Mikro(~),
(Ab)-Treiben,
Treibarbeit

cupellatie /
micro(~)

coupellation /
micro(~)

coppellazione /
micro(~)

copelación /
micro
(~)

купелирование / микро(~) /
к
упеляция

капельный метод

hallmark (-ing)

Punzierung

waarmerk / keur
rijksstempel

poinçonnage
poinçon de l’État

punzonatura /
bollatura, bollo

punzonado
contraste

пуансон / пробирное клеймо

touchstone /
touchstone test

Probierstein /
Strichprobe

toetssteen /
toetsstreek

pierre de
touche, touchau

pietra di
paragone

piedra de toque /
prueba de toque

пробирный камень / проба на пробирном камне

 

 

 Fire Assay

Bibliography:

Important
Articles
     &
Papers

(free download)

ANALYTICAL METHODS FOR DETERMINATION OF GOLD ( Articles & Papers ):

Articles from Word Gold Council (WGC)

◊ Assaying of Gold Jewellery - Review of Methods for Measuring Gold Content

◊ Gold Analysis - Comparisons of available Techniques

Articles from  ►"Gold Technology"  Magazine (WGC)

◊ "Assaying of Gold Jewel. - Choice of Technique" (GT, nº 32, 2001)               Dr. C. W. Corti

◊ "Analysis of Carat Gold"                             (GT, nº 22, Jul. 1997)                                 M. Brill

◊ "Assaying and Hallmarking in London"         (GT, nº 3, Jan 1991)                        D. W. Evans

◊ "Assaying Gold in Switzerland"                   (GT, nº 3, Jan 1991)       Wälchi / Vuilleumier

◊ "Touchstone Testing of Precious Metals"     (GT, nº 3, Jan 1991)       Wälchi / Vuilleumier

Articles from ►"Gold Bulletin" Journal (WGC)

◊ "Analysis of Gold. A Review of Methods"          (GB, Vol. 13, issue 1)       Roland S. Young

Articles from the ►"Alchemist" Journal , (LBMA)

◊ "The Art & Science of a Precious Metal Lab."      (Alch., nº 48, LBMA)               David Court

Articles from "Pure & Applied Chemistry" Magazine"

◊ "Analytical Chemistry of Noble Metals" (Pure & Appl. Chem., Vol. 49) Dr. Jon Cl. van Loon

 

 

Context: ►Assay Ton  ►Blank  ►Steps   ►Feathers  ►Matte/Speiss  ►Colours  ►Spitting  ►Sprout  ►Surcharge  ►Inquart  Hallmark  ►Cupels

Terms: ►Cupellation  ►Fire Assay  ►Reagents  ►Other Methods  ►Metals Sheets: ►Cupels  ►Crucibles  Index: ►Programme