1808 Contemporary Circulating Counterfeit Eight Reale. GNL Unlisted. Class 2. 39.0 mm. 25.9 grams as compared to 26.5 regal. Lima Mint. JP Assayer. Extremely Crude Edge Type (See GNL Types page 73 and in some ways almost as crude as the GNL Type 1 triangularedging punch. XRF Analysis indicated: Copper (9.45%), Silver (90.12%), Lead (0.13%), Mercury (0.1%), Zinc (0.02%) and Gold (0.2%). Ex. Gord Nichols.
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Keywords: Faux, Forgery, Unofficial, Contemporary Circulating Counterfeit, Falsa.
Trace Gold by Robert Gurney
The 100 ppm level of accuracy will detect silver that wasrefined in Mexico before 1870. All such silver MUST have an absolute minimum of200 ppm of gold. Here are the reasons I believe in this test stated as simply and clearly as Ican. This is the first time I have attempted a complete recitation of the factsknown to date. It is an updated position that I first discussed in what wouldbecome my book in 2014. The reliability of this test is based on the fact that silver and gold aremutually soluble metals. That is a rare characteristic for metals. Mostmetallic elements when mixed or melted together will not form homogeneoussolutions. When melted and then slowly cooled, the heaviest metal will tend tosettle to the bottom of a crucible. But in the case of gold and silver theyactually dissolve - they do not simply mix. When heated to a liquid state goldand silver form a solution similar to sugar that sweetens an entire cup ofcoffee - no amount of settlement will allow all the gold to settle out of aningot of silver. This simple fact is the reason why repeated fire cupellation ultimately did notwork to completely purify either gold or silver. In the early 1800s science hadnot yet determined exactly why that was. But there was a point beyond which noamount of cupellation worked. That is the gold trace we are looking for. Cupellation is a very old technique - used since pre-historic times to refine silverand gold. The process was successful at removing other impurities and metals byoxidation. In parting (the separation of gold from silver) cupellation reliedon the belief that the density of the two metals would divide the gold(heavier) from the silver (lighter). It was believed that cupellation causedthe heavier gold to completely disassociate from the silver and then the goldwould be free to fall by gravity to the base of the cupel where a button ofgold of increased purity would form beneath a button of increasingly puresilver. Therefore repeated cupellation of the products of the first cupellation wasthought to increase purity. After 5-7 repeats it was believed that pure silverand gold resulted. Repeated cupellation only an increase the purity of the goldand silver themselves from the presence of other contaminants like copper andlead but not from each other. Before 1850 it was actually impossible to purify either gold or silver tobetter than 99.5% pure on an industrial scale. In laboratories small amountsgold could be purified to almost 99.99% pure by using acids to remove smalltraces of silver. This was based on the fact that gold does not dissolve innitric acid but silver does. However there was no such process available for theremoval of a small trace of gold (a few percent at most) from silver. In most cases in Mexico, there was a limited amount of available fuel. Many ofthe mines and refineries were in remote often high desert areas - even if theywanted to perform multiple cupellation - it was impossible or at least it wasnot economical to do so. In that case raw refined silver went to the mint forrefining there. When the raw silver got to the mints, the economic situation was often nobetter. Fuel was still costly and in short supply. This created a financiallimit which the mints could not ignore. They could not spend more moneyto remove the gold than the gold itself was worth. This break evenpoint is why at times much more gold was left in the silver than at others. There was another issue as well. Cupellation takes time as well as trainedpeople to complete and in periods when the mints were stressed by the need tomake coins quickly (as in War time when soldiers needed to be paid) the valueof the output of money (coin)outweighed the small amount of gold that might berecovered. So during the War for Independence there was virtually no effort toremove the trace of gold.So at this point, people following the argument will possibly believe that allsilver worldwide had the same problem and that all of it will contain gold.That is not the case either. Most old world silver deposits were produced as aby product of lead mining. Argentiferous lead deposits were the most commonfound in Europe and gold was not present in significant amounts. Earlier workeddeposits of Electrum would be similar to Mexican silver but in the 1700-1900period no production from deposits of electrum or electrum like ores is notedas existing. New world deposits of silver were different then men had encountered earlierand these ores required a new technique to refine. The solution was usingmercury amalgamation. The patio process was the answer and it was invented byBartolomé de Medina in Pachuca, Mexico, in 1554. This process was superior toanything used in Europe. In Mexico, all of the silver is found in veins of quartz that intruded into therock strata during subsurface volcanic activity millions of years ago. Theuplift that formed the mountains of central Mexico is part of a single system.These major deposits run from southern Mexico into California and Nevada. Thesingle contaminant that is important to us in this uplift is gold. It makessilver from these mines essentially different from most other major depositsworldwide.The veins of Peru and Bolivia were created in a similar fashion at differenttimes in geologic history. Peru, Bolivia and Mexico are each on differenttectonic plates. So each uplift has a different elemental composition. InBolivia and Peru another trace contaminant arsenic is always involved and iscritical to determining authenticity. So it is possible to isolate silverproduced from these three uplifts by identifying the simple differences intrace contamination. Most of the data I have seen in this area come fromWinturthur Lab reports used by the Museum to authenticate early rare silverartifacts. Since gold is the primary contaminant of Mexican silver it is always present insilver that was mined and refined in Mexico before a process existed to removethe trace of gold.Based on over 200 tests performed so far, typically we have seen gold in the400 to 2000 ppm range. There are higher results for the early years of theMexican Republic with some test results as high as 3.8%. That is 38,000 ppm andwas observed on an 1836 Eight Reale from Guanajuato. I believe this could meanthat at times the early Republican mints did not bother removing the gold atall. There are also a very few results (less than 5 that I know of) where apparentlygenuine coins based on visual clues or die matches have yielded slightly lowerresults than 400 ppm. A test of 320 is the lowest I have seen personally on acoin from my collection. All of the lower measurements are seen on coins thatvisually have clues which identify them as fakes. So out of an abundance of caution, I call anything UNDER the 200 ppm level asilver COUNTERFEIT. I am very comfortable with that and have no doubt thatcoins below this level could not have been made before 1870 in Mexico. Between200 and 400 I personally classify the coins as \"suspicious\" orpossibly counterfeit. This limitation may condemn a very few coins to the suspect bin - but I thinkit is much better to do that than for all of the low gold coins to beconsidered GENUINE as they are now by 99% of dealers and collectors. Over time,as the science is more generally understood and accepted - I would hope that amore reasonable limit of 400 ppm would be adopted. However, for now 200 ppmmakes more sense and it will identify 97% of the target coins. There are other trace contaminants that can be very useful as well, that wouldinclude Antimony, Arsenic, Bismuth, Cadmium, Cobalt, Chromium, Iridium, Iron,Lead, Manganese, Mercury, Platinum, Tin, Titanium, Tungsten, Yttrium, Zinc anda few others that are more rare.
Patio Process - Silver Extraction
The Patio process was developed and used to refine both silver and gold in the 15thcentury, principally in the European silver mines that were producing silver for Venice(Vilar, 1976). The process was first described in 1540 by Biringuccio in De LaPirotechnia and is notably missing from Agricola’s 1556 publication De Re Metallica.Biringuccio, however, seems to have described the mercury amalgamation as a smallscale solution to recovering precious metals from slag and sweepings, rather than aprimary method of silver extraction (Biringuccio, 1540).
The Patio process was introduced to Mexico in 1556 by the German Gaspar Lomann andwas followed a year later by the Spaniard Bartolome de Medina who is most oftencredited with the introduction of the process to the New World (Vilar, 1976). Medina wasinstructed in the process in Spain by a German known as Lorenzo as follows;
Grind the ore fine. Steep it in strong brine. Add mercury and mix thoroughly. Repeatmixing daily for several weeks. Every day take a pinch of ore mud and examine themercury. See? It is bright and glistening. As time passes, it should darken as silverminerals are decomposed by the salt and the silver forms an alloy with mercury. Amalgamis pasty. Wash out the spent ore in water. Retort residual amalgam; mercury is driven offand silver remains (Probert, 1997).
Medina then spent two years in Pachuca experimenting with the process with mixedsuccess due to the different silver ore compositions from Europe to the Americas beforesuccessfully adapting the process to the local silver-rich, polymetallic ore (Zavala, 1962).
The process was then introduced at Potosí in 1570 by the Viceroy Francisco de Toledo,where silver production increased by 800 per cent in a decade as a result (Vilar, 1976).
The rate at which the process was adopted in Spanish America was rapid, which can begauged by the amount of mercury being imported from the Almaden mercury mine inSpain to be used in the process at the time. During the period 1550-1556, 40,370kg ofmercury was imported, increasing to 136,080kg during 1561-1565 (Vilar, 1976). Whenthe Huancavelica mercury mine in Peru began large-scale operations in 1563, theabundance of mercury available for silver extraction in Spanish America meant thatminimal effort was put into recovering used mercury for further use. As a result, it isestimated that up to 200,000 tons of mercury evaporated into the atmosphere or washeddown rivers in Spanish America during the use of the Patio process from 1556 to the1880s, causing long term environmental impacts (Pirrone et al., 1998).
The process, as briefly discussed by Lorenzo (Probert, 1997), consists of crushing the orein brine (salt water) to make a fine paste, and mixing it with mercury. Copper sulphate isadded as a later refinement to the process. The resulting paste was then spread out in ashaded area (generally on a patio) to about 30-60cm thick, and further mixed by mules,horses or occasionally people walking through it over a period of several weeks. At thispoint, the silver would have formed an amalgam with the mercury and could be recoveredfrom the rest of the ore (Dennis, 1963). The silver was then extracted from the amalgamby heating and evaporating the mercury (Vilar, 1976). The amount of mercury lost duringthe whole process was between one and two times the mass of the silver recovered(Egleston, 1883).
The Patio process can be described using the following equations. Silver sulphides arefirst converted to silver chloride, before the mercury reduces the silver chlorides toelemental silver, which is then amalgamated by the excess mercury. The elementalsulphur produced will also combine with the mercury to create cinnabar (Hg2S) (Johnsonand Whittle, 1999).
Ag2S(s) + 2Cu2+(aq) + 8Cl-(aq) → 2AgCl(s) + 2[CuCl3]2-(aq) + S(s)
(n + 2)Hg(l) + 2AgCl(s) → Ag2Hgn(l) + Hg2Cl2(s)
The process is now understood to be equivalent to hydrometallurgical chloride leaching,in which metal sulphide ores, which have been reacted with chloride ions in brine (NaCl),are oxidised by air in the presence of coppers salts acting as a catalyst. The oxidationprocess is continuously regenerated by the constant agitation of animals and humanswalking through the mix and breaking it up to expose new surfaces to the air (Johnsonand Whittle, 1999).
The Patio process was the principle method of silver extraction until the adoption in the1880s and 1890s of the MacArthur-Forrest process for extracting gold and silver fromores using cyanide extraction (Scheidel, 1894).
