Oxidation Roasting of Fine-Grained Carbonaceous Gold Ore: The Effect of Aeration Rate

The oxidation roasting of carbon-bearing micro-fine gold can eliminate or weaken the robbing effect of carbonaceous materials and clay, and destroy the encapsulation of micro-fine gold. The micropores produced by gas escaping during the roasting process are conducive to the diffusion of leaching agents, thus enhancing the cyanide leaching of gold. In this paper, the influence of the aeration rate during roasting on the leaching rate of fine-grained carbonaceous gold ore and its mechanism were studied using thermodynamic calculations, crystal structure analysis, surface chemical groups and bonds analysis, microporous structure analysis, and surface morphology detection. Under suitable roasting conditions, the carbonaceous and pyrite in the ore are oxidized, while carbonate minerals such as dolomite and calcite as well as clay minerals are decomposed, and the gold-robbing materials lose their activity. The experimental results have theoretical and practical significance for the popularization and application of oxidation roasting technology of fine carbon-bearing gold ore.

KAJI ULANG SNI 13-3487-2005 BARANG – BARANG EMAS DAN SNI 13-3771-1995 BARANG – BARANG EMAS MUDA

<p>Emas merupakan logam mulia yang dapat dijadikan investasi karena nilainya terus naik dari waktu ke waktu. Barang – barang emas dapat berbentuk batangan, granula, lembaran, perhiasan dan benda seni. Penjaminan mutu kadar emas diatur dalam SNI 13-3487-2005 Barang – barang emas dan SNI 13-3771-1995 Barang – barang emas muda. Pada saat ini emas yang beredar memiliki kadar mulai 3,33% hingga 99,99% (<em>fine gold</em>). Terdapat nilai kadar emas yang belum diatur dalam ke-dua SNI tersebut yaitu barang-barang emas dengan kadar 13,14,15,dan 16 karat. Sehingga perlu dilakukan pengujian untuk melihat kesesuaian kadar emas yang terkandung dalam barang – barang emas yang beredar di pasaran serta peninjauan kembali terhadap metode uji yang ada. Penelitian ini membahas hasil kaji ulang SNI 13-3487-2005 Barang – barang emas dan SNI 13-3771-1995 Barang – barang emas muda sebagai dasar penyusunan SNI barang – barang emas yang baru. Metode penelitian yang dilakukan adalah studi literatur, pengujian sampel barang – barang emas yang beredar yang diambil secara <em>purposive sampling</em>, kemudian dilakukan pengujian <em>fire assay</em> sesuai dengan SNI 13-3487-2005 Barang – barang emas dan ICP-OES sesuai dengan ISO 15093, <em>Jewellery — Determination of precious metals in 999 0 / 00 gold, platinum and palladium jewellery alloys</em> — <em>Difference method using ICP-OES</em>, kajian metode uji, dan penggalian informasi melalui rapat internal, rapat teknis dan rapat konsensus. Berdasarkan pembahasan maka dapat disimpulkan bahwa perlunya penggabungan dua SNI tersebut mencakup kadar 33,3% hingga 99,99%, menetapkan metode uji yang dipergunakan yaitu <em>fire assay</em> dan ICP-OES, dengan acuan normatif yang dipergunakan adalah standar ISO 11596 dan ISO 15039.</p>

Gold in a Woman’s Burial Costume of the Late Ancient Bosporan Elite: New Materials from Phanagoreia

This paper publishes a unique woman’s costume with gold ornaments from the Hunnic Period. This find originates from a burial vault in Phanagoreia dated back to the late fourth or early fifth century AD. There are numerous gold foil badges uncovered in situ on a woman’s neck and chest. They were sewn on the collar of a robe and an outer garment. Gold ornaments appeared only on the front side of the cloths to be seen by the funeral ceremony participants. The find of the ornaments in Phanagoreia contributes to the suggestion that there was a universal set of gold ornaments for cloth in the Hunnic Period. It has been inferred that the costume decorated with fine gold ornaments played ceremonial role. It was made especially for funerals of noble and rich women belonging to the Bosporan elite. However, the culture of the barbarians living in the vicinity of the Bosporan Kingdom in the Migration Period possibly developed alternative perception of the costume in question

Prospects for Degdekan Gold Project in the North-East of Russia

The article describes the analytical, mineralogical and technological studies into enclosing rocks of Degdekan gold deposit. It is found that ore composition is dominated by silicon oxide (62.2–70.4 %), the ore-forming minerals are mainly iron, sulfur and arsenic in sulfide and oxide forms. The clustering analysis distinguishes three representative geochemical associations: Au-Ag-Pb-Sb; As-Mo-Cu; Co-Ni-Cr-Zn-W. Mineralization is pyrite, arsenopyrite, free gold, seldom fahlore, pyrrhotine, chalcopyrite, galena, sphalerite, etc. Pyrite contains As and Ni impurities. By the criteria of association and recovery, gold is present in 4 varieties: free gold recoverable by amalgamation and cyanation; fine gold associated with sulfides and disengageable after oxidizing roasting; fine and very fine gold associated with iron hydroxides, carbonates and chlorites, and extractable in cyanation after HCl treatment; fine gold associated with carbon black and recoverable by cyanation after oxidating roasting at a temperature of 650 °C. The bulk (from 41.6 to 86 %) is represented by free gold extractable in cyanation and gravity separation. This gold features large particles and occurs at the zones of quartz veins, both in veins and in strings. Percentage of fine gold (–0.04 mm) in metasomatic quartz–cericite rocks (nearby veins) varies from 2 to 11 %. There are also platinoid group metals, highly concentrated in sulfide concentrates. Potential resources of platinoids as associated metals are estimated as 10 t (around 10 % of gold resources). The authors arrive at the conclusion on feasibility of joint concentration of gold and platinoids in an integrated process circuit by gravity separation with end product as a Doré bar containing platinoids.

Corrosion of titanium implants and connected prosthetic alloys using lactic acid immersion test

Background/purpose: Combination of dental titanium implants with other prosthetic metallic components may lead to metal ion release that increases the risk of adverse reactions in patients. The present study therefore aimed to determine in vitro metal ion dissolution from different alloy combinations. Materials and methods: Dental alloys were subjected to a lactic acid immersion test together with titanium implants and matched with controls. Between day 1 and 38, open direct current potentials (DCP) between the samples and the electrolyte were recorded and metal dissociation inside the electrolyte was assessed using ICP-MS. Results: Absolute DCPs of the different alloys increased significantly (p<0.001) from 100-150mV to 490-580 mV within the first two weeks of immersion, dropping to about 450mV later on largely independent of the material. Titanium showed highest dissociation rates (2.00-12.06µg/cm2 per day; p=0.0002); all other components demonstrated poor corrosive dissolution (<0.6µg/cm2 per day). After immersion of 38 days, titanium still yielded high dissociation (0.64-1.38µg/cm2 per day) for all test groups. Presence of fine gold inside the electrolyte significantly increased dissociation of titanium (p=0.027). Dissociation of iron indicated contamination from tool components used for implant production. Optical examination of non-precious metal surfaces showed no corrosive discoloration after 5 or 26 weeks of lactic acid immersion. Conclusion: Within the limitations of this study, there is no objection against the use of non-precious alloys for the fabrication of components and prostheses supported on titanium implants if gold is not present inside the same electrolyte.

Fine Gold Extraction Problem from Industrial Sludge

Error reasons of gold analytical determination in the chemical plant sludge are studied. The studied sludge is waste of BaCl2 production. According to preliminary estimates it contains gold in sufficient quantity for industrial extraction. Comparison of direct sludge fire assay analysis and sludge dissolution in aqua regia, followed by gold atomic absorption determination in solution is made. The negative effect of Na+, Ca2+, Ba2+, Zn2+ ions presence in studied solutions was shown. Error quantitative estimate at alkali metals introducing into standard solutions is given. It is shown that Ca2+ and Ba2+ ions contribute the most error. Error increases linearly at addition of Ca2+ and Ba2+ ions. Growth error gradually slow down at increasing Na+, Zn2+ ion content.