History of Fire Assaying
Fire Assaying is an ancient and time-honored Art/Science which determines the precious metal content in ores, metallics, solutions and all other materials bearing Gold and Silver. It is a branch of analytical, inorganic chemistry which has as its object the quantitative determination of values in small amounts of material which represent much larger amounts of the same material. The method is accomplished by using a combination of intense heat, dry reagents or fluxes, and specialty vessels to separate the precious metals from the rest of the extraneous material. The final outcome is achieved in what is usually a two or three step process, depending on the complexity of the starting material.
The steps are defined as Scorification and Cupellation; the former is the process which gathers the metals into a workable form and the latter the technique by which the non-precious, or base metals are Oxidized away, leaving the precious metals behind.
The Fire Assay method, which is still most widely
viewed as the most accurate means of determining Gold and Silver content, has been altered very little over the centuries. Its origins can be traced as far back as the Bible:
I have made you an assayer and tester among my people
That you may know and assay their ways
They are bronze and iron, and they act corruptly
The bellows blow fiercely, and the lead is consumed by the fire
In vain the refining goes on; refuse silver they are called
For the Lord has rejected them
Jeremiah 6:27-30
Assaying began to appear in literature in the 12th century in France and England, and over time spread to the rest of Europe. One of my favorite passages about it is from a 1556 A.D. text called De Re Metallica by Agricola which states:
It is necessary that the assayer who is testing ore or metals should be prepared and instructed in all things necessary in assaying, and that he should close the doors of his room in which the assay furnace stands, lest anyone coming in at an inopportune moment might disturb his thoughts when they are intent on work.
While extreme for this day and age, this nevertheless points out the degree of diligence which must be paid to the work at hand.
The practice of assaying is empirical in nature; results and conclusions are based on observations and experience gained through years of testing, and the reproducibility of results is of paramount importance. Duplicate and triplicate samples are always run to ensure these results.
The dedicated assayer should never get to the point where there is nothing more to learn. Interesting nuances constantly present themselves, even in frequently tested materials, and so the day to day workings remain fascinating to the fire assayer who is committed to his craft.
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Specializing in the fire assay of gold & silver
Ed Brennan, Lab Manager
105 Dexter Road
PO Box 14040
East Providence, RI, 02914
Phone/Fax 401-434-3337
Email at: assayone@aol.com
Assay One is a fire assaying lab that specializes in:
fire
assaying
material
analysis
quality
control testing of metals
analysis
of gold samples
analysis
of silver samples
sterling
silver analysis
ion
exchange resin analysis
monitoring
of plating solution
Umpire analysis