Characterization of an iron oxy/hydroxide(gossan type) bearing refractory gold and silver ore by diagnostic leaching

A detailed characterization of an iron oxy/hydroxide(gossan type) bearing refractory gold/silver ore was performed with a new diagnostic approach for the development of a pretreatment process prior to cyanide leaching. Gold was observed to be present as native and electrum(6-24 μm in size) and associated with limonite, goethite and lepidocrocite within calcite and quartz matrix. Mineral liberation analysis(MLA) showed that electrum is found as free grains and in association with beudantite, limonite/goethite and quartz. Silver was mainly present as acanthite(Ag2S) and electrum and as inclusions within beudantite phase in the ore. The cyanide leaching tests showed that the extractions of gold and silver from the ore(d80: 50 μm) were limited to 76% and 23%, respectively, over a leaching period of 24 h. Diagnostic leaching tests coupled with the detailed mineralogical analysis of the ore suggest that the refractory gold and silver are mainly associated within iron oxide mineral phases such as limonite/goethite and jarosite-beudantite, which can be decomposed in alkaline solutions. Based on these characterizations, alkaline pretreatment of ore in potassium hydroxide solution was performed prior to cyanidation, which improved significantly the extraction of silver and gold up to 87% Ag and 90% Au. These findings suggest that alkaline leaching can be used as a new diagnostic approach to characterize the refractoriness of iron oxy/hydroxide bearing gold/silver ore and as a pretreatment method to overcome the refractoriness.

GOLD AND SILVER WINGED GODS FROM THE TUBO PERIOD

Ethnic people living on the Tibetan Plateau during the Tubo period have been well-known as not only strong and brave on horses,but they were also an ethnic group enriched with powerful creativity and rich imagination.From Tubo’s cultural art,we can observe a large amount of extremely fine artifacts.For instance,among

Box with inlaid gold and silver cloud patterns

The late Warring States Period (475 B.C-221 B.C)Caliber diameter:18.2 cm Bronze with inlaid silver The surfaces of the utensil body and the lid are decorated with cloud patterns by using the inlaid gold or silver filaments and flakes. The decorative patterns are very slim and extremely exquisite.

Comparative study of the effects of gold and silver nanoparticles on the metabolism of human dermal fibroblasts

The purpose of this article was to explore the effects of gold nanoparticles(GNPs)and silver nano-particles(SNPs)with different cytotoxicities on human dermal fibroblasts(HDFs)at the metabolic level.First,~20 nm of GNPs and SNPs were prepared,and their effects on the proliferation of HDFs were evaluated.Then,a metabolomics technique was used to analyse the effects of GNPs and SNPs on the expression profiles of metabolites in HDFs after 4,8 and 24h of treatment.Furthermore,the key metabolites and key metabolic pathways involved in the interaction of GNPs and SNPs with HDFs were identified through expression pattern analysis and metabolic pathway analysis of differentially expressed metabolites and were finally verified by experiments.The results of the cytotoxicity experiments showed that there was no cytotoxicity after the treatment of GNPs for 72 h,while the cytotoxicity of the SNPs reached grade 1 after 72 h.By using metabolomics analysis,29,30 and 27 metabolites were shown to be differentially expressed in HDFs after GNP treatment,while SNPs induced the differential expression of 13,33 and 22 metabolites after 4,8 and 24h of treatment,respectively.Six and four candidate key metabolites in the GNP and SNP groups were identified by expression pattern analysis and metabolic pathway analysis,respec-tively.The key metabolic pathways in the GNP and SNP groups were identified as the glutathione metabolic pathway(the key metabolite of which was glutathione)and the citrate cycle pathway(the key metabolite of which was malic acid).Based on the experiments used to verify the key metabolites and key metabolic pathways,it was found that the increase in glutathione after GNP treatment might trigger an oxidative stress protection mechanism and thus avoid cytotoxicity.After exposure to SNPs,the citric acid content was increased,mainly through the citrate cycle path-way,thereby inhibiting the synthesis of malic acid to affect the formation of ATP and finally leading to cytotoxicity.

Gold and Silver Inlaid Bronze Sheep

Gold and silver inlaying is a metal processing technique popular during the Spring and Autumn Period (770-476 B. C.) and the Warring States Period (475-221 B. C.). Patterns on the surface of the bronze figure are chiselled out and gold and silver threads (which can be as thin as hair) are inlaid. Finally the whole figure is filed and polished resulting in a splendid artistic work highlighting the different colours of the three different kinds of metal. The artifact shown here was unearthed from Ningxia'...