Sending Laurion Back to the Future: Bronze Age Silver and the Source of Confusion

Silver-bearing lead ores at Laurion in Attica were considered to have been first exploited with the introduction of coinage sometime around the birth of Classical Greece. However, in the late 20th century this chronology was radically revised earlier, to the Bronze Age, largely supported by lead isotope analyses (LIA). Here, we acknowledge that lead and silver metallurgy emerged from the earliest times but we propose that any correlation between these metals in the archaeological record is not a consequence of a geological association between lead and silver in ores such as galena until the middle of the first millennium BCE. We suggest that ancient metallurgists recognised that silver minerals (such as horn silver) dispersed in host rocks could be concentrated in molten lead and that LIA signatures of Bronze Age silver artefacts reflect the use of exogenous lead to extract silver, perhaps applying processes similar to those used to acquire silver in Bronze Age Siphnos. We further propose that lead from Laurion used for silver extraction resulted in the inadvertent transfer of its LIA signature (probably aided by roving silver prospectors) to silver objects and metallurgical debris recovered around the Aegean. New compositional analyses for the Mycenaean shaft-grave silver (c. 1600 BCE) support these conclusions. We believe that reverting to the mid-first millennium BCE for the first exploitation of silver from argentiferous lead ores is consistent with the absence of archaeological evidence for centralised control over Laurion until the Archaic period, the paucity of lead slag associated with silver-processing debris at Bronze Age sites, the scarcity of silver artefacts recovered in post-shaft grave contexts at Mycenae and throughout the Early Iron Age Aegean, the few Attic silver coins with LIA signatures consistent with Laurion until after 500 BCE and a single unambiguous mention of silver in the Linear B texts.

On the variability of technological indicators in the extraction of precious metals

in the conditions of significant variability of processed polymetallic ores of the Akbastau Deposit, it is essential to minimize the variability of technological indicators of enrichment. Due to the multifactorial nature and non-linearity of the flotation process, the use of classical regression models does not provide the necessary level of reliability, therefore, there is a significant variability in the extraction of precious metals. To solve this problem, the paper substantiates the use of the neural network modeling methodology, which allows to estimate the variability of gold and silver extraction depending on the variation of the content of metals in the ore.

Sº and jarosite behavior during recovery of values from the direct leaching residue of sphalerite using cyanide and glycine

This paper reports the effect of the components of a direct leaching residue (jarosite and elemental sulfur), on the recovery of valuable metals such as gold and silver. Leaching media such as cyanide and mixtures of cyanide with glycine were used to recover the gold and silver from the residue; however, a low recovery of these metals was obtained. The above due to the negative effect of its components which cause problems in the extraction process such as encapsulation of silver (due to jarosite) and the formation of thiocyanate and re-precipitation of silver (due to sulfur). Various treatments prior to leaching were tested, finding that when the residue is desulfurized with perchlorethylene and subjected to an oxidizing alkaline hydrothermal treatment, the gold extraction increased from 39.73 to 88% and the silver extraction of 64.76 to 94.29%. Additionally, it was determined that when cyanide is assisted by glycine, the latter decreases the cyanide consumption by inhibition of the dissolution of iron and sulfur in cyanide.

Pengaruh Penambahan H2O2 dan Na2S2O5 pada Proses Detoksifikasi Tailing Hasil Pelindian Emas

Abstrak. Proses ekstraksi emas dan perak melalui metode pelarutan selektif menggunakan reagen sianida merupakan proses pengolahan yang umum digunakan saat ini. Salah satu tantangan yang hadir dengan pemanfaatan proses pelindian adalah kontrol kandungan weak acid dissociable cyanide (WAD CN) pada tailing hasil proses pelindian guna menghindari terjadinya pencemaran lingkungan. Berdasarkan standar yang ditetapkan oleh International Cyanide Management Institute (ICMI), kandungan sianida yang diperbolehkan untuk dibuang bersama tailing ke lingkungan sebesar <50 ppm. Rangkaian proses yang harus dilakukan untuk menekan kandungan WAD CN pada tailing adalah melalui proses cyanide detoxification. Proses detoksifikasi yang dilakuan adalah dengan menambahkan oksidator berupa H2O2 dan kombinasi dengan Na2S2O5 (sodium metabisulphide/SMBS) dengan rasio H2O2:CN sebesar 2:1, 5:1, 10:1, dan 20:1, serta penambahan SMBS dengan rasio antara SO2:CN sebesar 4:1 dalam sebuah bottle roll. Penambahan SMBS bertujuan untuk menurunkan jumlah penggunaan oksidator H2O2 yang digunakan. Berdasarkan analisis yang dilakukan diketahui bahwa semakin besar perbandingan antara H2O2:CN maka semakin rendah WAD CN yang dihasilkan, dari 84 ppm sebelum adanya penambahan oksidator menjadi 0,18 ppm pada rasio penambahan 20:1. Selain itu penambahan Na2S2O5 juga menyebabkan penurunan kandungan WAD CN yang lebih signifikan menjadi 0,31 ppm pada rasio H2O2:CN sebesar 5:1. Adapun variasi pH tidak menunjukkan pengaruh yang signifikan terhadap kadar WAD CN pada saat proses detoksifikasi. Kata kunci: sianidasi, detoksifikasi sianida, wastewater treatment, pelindian emas. Abstract. The Effect of H2O2 and Na2S2O5 Addition in Cyanide Detoxification from Leached-Gold Tailing. Cyanide leaching is the predominant process of gold and silver extraction in large scale mining. The most challenging part related to leaching process of cyanide is controlling the content of weak acid dissociable cyanide (WAD CN) in tailing to prevent environmental pollution. The International Cyanide Management Institute (ICMI) has determinded the cyanide content allowed to be disposed of with tailings into the environment should not more than 50 ppm. Content of WAD CN in tailing can be suppressed by cyanide detoxification process. Detoxification process was conducted by adding H2O2 as an oxidizing agent into the tailings with varying H2O2:CN ratio (2:1, 5:1, 10:1, and 20:1) and combining with the addition of Na2S2O5 (sodium metabisulphide/SMBS) with SO2:CN ratio of 4:1 in a bottle roll. The study showed that the greater the ratio of H2O2:CN, the lower the WAD CN remained in tailing, from 84 ppm before any addition of oxiding agent to 0.18 ppm at ratio of 20:1. Moreover, Na2S2O5 addition was also significantly reduced WAD CN content down to 0.31 ppm at H2O2:CN ratio of 5:1. It also has been identified that pH variation has no significant impact to WAD CN content during detoxification process. Keywords: cyanidation, cyanide detoxification, wastewater treatment, gold leaching. Graphical Abstract