• Corrosion Science and Technology
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• v.6 no.6
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• pp.304-307
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• 2007

As to the reflection electrode of LCD (liquid crystal displays), silver-copper-gold alloy (hereafter, it is called as ACA (Ag98%, Cu1%, Au1%)) is an effective material of which weathering resistance can be improved more compared with pure silver. However, there is a problem that gold remains on the substrate as residues when ACA is etched in cerium ammonium nitrate solution or phosphoric acid. Gold can not be etched in these etchants as readily as the other two alloying elements. Gold residue has actually been removed physically by brushing etc. This procedure causes damage to the display elements. Another etchant of iodine/potassium iodide generally known as one of the gold etchants can not give precise etch pattern because of remarkable difference in etching rates among silver, copper and gold. The purpose of this research is to obtain a practical etchant for ACA alloy. The results are as follows. The cyanogen complex salt of gold generates when cyanide is used as the etchant, in which gold dissolves considerably. Oxygen reduction is important as the cathodic reaction in the dissolution of gold. A new etchant of sodium cyanide / potassium ferricyanide whose cathodic reduction is stronger than oxygen, can give precise etch patterns in ACA alloy swiftly at room temperature.

• Economic and Environmental Geology
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• v.23 no.2
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• pp.183-199
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• 1990

Ore deposits of Dongwon mine are composed of numerous gold and silver veins emplaced in sedimentary rocks of Cambrian Choseon Supergroup and granitoids of Cretaceous age. Ore veins of the mine can be divided into gold and silver veins on the base of vein structure, mineral assemblage and vein trends. Mutual relationships between gold and silver veins are uncertain. Gold veins are simple veins which are composed of base-metal sulfides, and electrum with quartz and ankerite. On the other hand, silver veins are complex veins which reveal three distinct stages of mineral deposition based on vein structure; stage I, deposition of small amounts of oxides and pyrite with quartz; stage II, deposition of base-metal sulfides, small amounts of Ag-bearing minerals, calcite and quartz; stage III, deposition of base metal sulfides, electrum, Ag-sulfosalts, native silver, carbonates and quartz. Homogenization temperature and salinity of fluid inclusion from quartz of gold vein are as follows; $229^{\circ}$ to $283^{\circ}C$, 4.7 to 6.4 wt.% equivalent NaCI. The ore mineralogy suggests that temperature(T) and sulfur fugacity($fs_2$) of the formation of the gold vein and stage III of silver vein are estimated as T ; $294^{\circ}$ to $318^{\circ}C$, $fs_2\;10^{-9.4}$ to $10^{-10.1}$ atm. and T; $240^{\circ}$ to $279^{\circ}C$, $fs_2;10^{-11.1}$ to $10^{-17.3}$ atm. respectively. Pressure condition during gold vein formation estimated from data of ore mineralogy and fluid inclusion range 500 to 750 bar.

• Economic and Environmental Geology
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• v.19 no.spc
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• pp.193-206
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• 1986

A number of auriferous veins occur in the Precambrian metamorphic terrain from Chungju to Mugeug district. These gold (-silver) deposits consist mainly of the fissure-filling quartz veins intruding the Precambrian gneiss or schist and Jurassic or Cretaceous granite. These gold (-silver) deposits can be 'divided into two mineralization epochs, (a) gold-rich veins related to Daebo igneous activity, and (b) gold-silver veins related to Bulgugsa igneous activity. These two groups of ore deposits with different generation can be characterized by the mode of occurrence of ore vein and the ore mineral associations. The auriferous quartz veins of Taechang and Boryeon mines associated with late Jurassic igneous activity are massive in character, and show the simple mineral assemblages and low Ag/Au ratio in the ores, representing a single mineralization system. The ore minerals are predominantly quartz containing minor or trace amonts of pyrrhotite, sphalerite, galena, pyrite, chalcopyrite and electrum. Electrum is closely associated with pyrrhotite and has chemical compositions from 61.4 to 78.5 atomic % Au. Fluid inclusion data suggest that ore minerals were deposited at temperatures between 238 and $390^{\circ}C$ from $CO_2$-rich fluids. The gold and/or silver-bearing quartz veins of Geumwang mine related to middle Cretaceous igneous activity are characterized by the multistage history, diverse mineral assemblages with high Ag/Au ratio in the ores. The ores of Geumwang mine have two contrasting mineral assemblages (1) pyrite+galena+sphalerite+arsenopyrite+electrum+argentite, representing the higher gold mineralization, and (2) pyrite+chalcopyrite+ galena +sphalerite+ arsenopyrite+silver sulfosalts+ electrum+ native silver+argentite, representing the higher silver mineralization. Electrum is closely associated with pyrite and has chemical compositions from 11.2 to 49.9 atomic % Au. The depositional environment during the higher gold mineralization can be estimated as the range of both temperature and sulfur fugacity, T= $200{\sim}300^{\circ}C$, log f ($S_2$) = $10^{-10}{\sim}10^{-15}$. The higher silver mineralization may be interpreted to have formed a range of falling temperature ($150{\sim}200^{\circ}C$) and low sulfur fugacity($10^{-10}{\sim}10^{-15}$). These temperature data are consistent with homogenization temperatures of fluId inclusions in quartz. Thus, the gold veins related to the Daebo igneous activity may be formed by the environment of higher temperature and pressure than the gold-silver veins associated with the Bulgugsa igneous activity.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.123-130
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• 2012

Leaching experiments of gold and silver from roasted concentrate were carried out using a chlorine-hypochlorite solution. The leaching rate of gold was 75% at 1.5:1 ratio of chlorine and hypochlorite and increased to 81% with adding 1 M NaCl. However, at 1% pulp density and at $65^{\circ}C$, the leaching rates of Au were close to 100%. XRD analysis identified quartz in the solid residues after digestion of roasted concentrate with aqua regia or chlorine-hypochloride leaching solution. This suggests that the gold may not be leached out of the quartz in aqua regia or chlorine-hypochlorite solution. In order to leach the gold from the quartz, the concentrate will have to be pre-treated through ultra-fine grinding or treated with stronger oxidative agents.

• Conservation Science in Museum
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• v.6
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• pp.31-37
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• 2005

The copper incense burner inlaid with gold and silver and purchased by the National Museum of Korea in 2002 was to be corroded severely throughout the surface. It was difficult to recognize the part with silver inlaying. Using the abrasive method with alumina, however, its splendid inlaying patterns were restored. Prior to applying the abrasive method, the quality was examined, and a material that could help bring out the patterns without causing too much damage to the artifact, selected. The overall condition of the incense burner was also checked through X-ray equipment to know the condition of the gold and silver inlaying, and by x-ray fluorescence spectroscopy to confirm the composition of the incense burner and gold and silver inlaying. The result of this process is expected to serve as valuable data in future research on incense burners inlaid with gold and silver.

• Economic and Environmental Geology
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• v.21 no.4
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• pp.389-400
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• 1988

Minor elements such as Ag, As, Au, Bi, Cd, Cu, Co, Ni, Pb, Rb, Sb, Sr and Te were analyzed by atomic absorption spectrophotometry and induced coupled plasma spectrophotometry in order to investigate pathfinders for gold in quartz porphyry, granite porphyry and vein materials in Jeonjuil gold - silver mine, and in altered biotite granites and vein materials in Dukum gold - silver mine. In Dukum gold - silver mine, it is observed that Au contents have positive relation with As, Co, and Rb contents, but negative relation with Bi contents in altered biotite granites. Au contents have positive relation with Ag, As, Co and Te contents in vein materials. In Jeonjuil gold - silver mine, it is observed that Cd, Rb, Sr and Te are enriched near ore vein in quartz porphyry and granite porphyry. Au contents have positive relation with As, Cd, Cu, $Fe_2O_3$ and $K_2O$ in vein materials.

• Economic and Environmental Geology
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• v.25 no.4
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• pp.379-395
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• 1992

The gold ore deposits of Nakcheon, Gongyeong and Dongmyeong mine in the Imgye district are E-W trending fissure filling veins emplaced in Precambrian Jungbongsan granite and sedimentary rocks of Cambrian Yangdeog group. The K-Ar age for vein alteration sericite and vein laced muscovite are 73 and 93 Ma, respectively. Vein structure and mineralogy indicate the three distinct depositional stages: I) basemetal sulfides and tin minerals, II) gold-basemeatl sulfides, III) gold-silver-basemetal sulfides. Major gold and silver ore minerals are electrum, native silver, pyrargyrite and argentite. Fluid inclusion data indicate that filling temperatures were from $350^{\circ}C$ to $190^{\circ}C$ through stage I, II and III. Salinities were in the range of 0.0~9.5 NaCl eq.wt.% and do not reveal any systematic trend. Intermittent boiling of ore fluid during stage I is indicated by fluid inclusions in quartz. Fluid pressure during stage I which is estimated from fluid inclusions showing boiling evidence range from 50 to 100 bars. Gold ore deposits of the Imgye district were formed under higher temperatures and lower sulfur fugacities compared with the Eunchi silver ore deposits about 8 Km apart from the Imgye district.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.56 no.4
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• pp.359-366
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• 2019

This article aims to summarize the recycling status of scrap gold, silver, platinum, and palladium by regions and industries in order to utilize the data for securing raw materials of the domestic urban mining industry. The amount of gold from scrap has shown a tendency to decrease in countries other than China over the last ten years, which is attributed to the increase in scrap containing gold in China. The industry demand for gold is the highest in electronic products, but it is decreasing. The amount of scrap recycling for silver has declined but total silver production has increased by increasing mine products. As production and demand from platinum and palladium scrap are mostly for catalysts, their demand could be affected by the electric vehicle industry.

• Korean Journal of Heritage: History & Science
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• v.52 no.1
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• pp.4-21
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• 2019

In this paper, 23 Silla gold earrings from the sixth and seventhand centuries, excavated from the Yeongnam region, were analyzed. Based on the silver content of the gold plate, they were classified into three types. The classifications included type I(20-50wt%), type II(10-20wt%) and type III (less than 10wt%). In the analysis process, the composition and morphological differences were identified on the surface of the gold plate. In the case of type I and II earrings, it was observed that the fine holes were concentrated in a relatively higher part of the gold content. The causes of the difference in the surface composition of the gold plate were divided into four categories: 1) surface treatment, 2) thermal diffusivity in the manufacturing process, 3) differences in composition of alluvial gold, and 4) the refining method of gold. It is possible that depletion gilding was attempted to increase the gold content while intentionally removing the other metals from the surface of the gold alloy in the portion where the gold deposit is relatively concentrated on the surface of the gold plating. The highest copper content was detected in the earring with the highest gold content of the analyzed earrings, and it was assumed that thermal diffusion had occurred between the gold plate and the metal rod during the manufacturing process rather than intentional addition. Copper was detected only in the thin ring earring type, and copper was not detected in the thick ring earring type or pendant type. It also proves that this earring has a high degree of tightness at higher temperatures, as there was an invisible edge finish on other earrings and horizontal wrinkles on the gold plate surface. In terms of the material of the gold plate, we examined whether the silver content of the gold plate was natural gold or added by alloy through analyzing the alluvial gold collected in the region. As a result of the analysis, it was found that on average about 13wt% of silver is included. This suggests that type II is natural gold, type III is refined gold, and type I seems to have been alloyed with natural gold. Here, we investigated the refining method introduced in the ancient literature, both at home and abroad, about the possibility of alloying silver after the refining process of type III earrings and then making pure gold. It was found that from ancient refining methods, silver which had been present in the natural gold was removed by reacting and combining with silver chloride or silver sulfide, and long-term efforts and techniques were required to obtain pure gold through this method. Therefore, it was concluded that the possibility of adding a small amount of silver in order to increase strength after making pure gold through a refining process is low.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.303-309
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• 2007

Statement of problem. The effect of gold electroforming on gold alloy was not studied. Purpose. This in vitro study investigate the effect of gold electroforming on gold-silver-palladium alloy. Material and methods. Three pieces of gold strips had undergone the electroforming procedures on one side and then half of the side again electroformed. The set mode for this study was program 1 ($200{\mu}m$). And the processing time was 15min (1/20 time to form $200{\mu}m$ coping). The confocal laser scanning microscope (PASCAL 5, Carl Zeiss, Bernried, Germany) was used to measure the thickness of the pure gold layer electroformed on the gold strips. Half of the gold strip was coated two times with electroformed gold, and the other half one time. The data from the cone focal laser system was processed to get the vertical profile of the strips and the difference of the vertical height between the double coated and single coated layer was regarded as the thickness of the gold coating. The layer thickness value to built 3D image of the cone-focal laser was set $0.5{\mu}m$. Next to the measurement of the thickness of the coating, the Vicker's hardness test was done. It was performed on the double coated surface, single coated surface and non-coated surface (back side) three times each. Results. The mean thickness value gained from gold electroforming technique was measured to be $22{\mu}m$ for sample 1, $23{\mu}m$ for sample 2, $21{\mu}m$ for sample 3. In the same condition of time, power and the amount of electrolyte, the data showed no difference between samples. According to the results of variance analysis, the differences among the variations in number of coating were statistically insignificant (p>0.05), meaning that the two times of gold electroforming coating did not change the hardness of gold-silver-palladium alloy. Conclusion. The test of thickness of gold coating proved the coherency of the gold electroforming procedure, in other words, when the power, the exposed surface area, processing time and the amount of electrolytes were set same, the same thickness of gold would be coated on. The hardness test showed that the electroformed gold coating did not change the hardness of the gold-silver-palladium alloy when it is coated not more than $45{\mu}m$.