Wednesday, 12 March 2014

Fascinating correlations between ancient and modern gold beneficiation techniques revealed

The "Ancients" certainly knew a thing or two. Just over 3 years ago (posting of 13 December 2010) I discussed the various theories proposing that the blocks comprising the Egyptian pyramids may not have been carved from stone quarries, but may have been cast into place using an artificial zeolite geopolymer. Now a fascinating open access article has just been published in Minerals Engineering, authored by Prof. Thomas Neesse of the University of Erlangen, Germany, a familiar face at many MEI Conferences.


Thomas Neesse (right) at Physical Separation '09 with
Erlangen colleague Johann Dueck
Ancient reports and mining relicts indicate that in antiquity technologies of high empirical level were used to enrich finely dispersed gold,  exhibiting interesting correlations with modern gold ore beneficiation. Neesse's review describes the scientific basis behind these beneficiation technologies and confirms their historical significance. All of these ancient processes operate on the principle of selectively attaching finely dispersed gold particles onto a solid collector material via hydrophobicity, chemisorptive bonding, or electrical surface charges. . New research provides scientific explanations for several ancient variants of gold ore beneficiation that are discussed in the paper, including the dry and wet attachment processes used in pharaonic Egypt, sheepskins utilized as gold collectors in the Caucasian region, hemp utilized as a gold collector in Celtic Bohemia, and the use of gorse for gold beneficiation in the Roman Empire. The highest performing antique gold beneficiation technique was the use of gorse as a superhydrophobic gold collector and can be regarded as a precursor to the modern flotation process.

Empirical knowledge of these sophisticated technologies appears to have existed since the 3rd millennium BC but could not have been explained until today, based on new research regarding the triboelectric properties of gold, its hydrophobic effects, and nanogold chemistry. Combining density sorting and attachment processes enabled the mining of gold-poor deposits containing finely dispersed gold.  The first biocollectors were high-oil-content woods and animal furs. Later, during the Celtic-Roman eras, mining was expanded to utilize hemp and gorse plant collectors. However, many of the details regarding these complicated processes will never be discovered.

Further, dry technologies with ancient origins (i.e., the plant uptake of gold and the triboelectric separation) may influence advancements in existing beneficiation technologies. Today, the plant uptake of gold, which is comparable to the ancient Celtic hemp process, is being evaluated in phytomining projects in arid regions. Hemp has not yet been tested but appears to be an interesting possibility because it combines hydrophobic attachment and the gold plant uptake under hydroponic conditions.

This is a fascinating article which should be read by all who have an interest in mining history, and particularly of gold processing.

3 comments:

  1. In INDIA age old process (1918 British rule in india) was adopted in a Govt. company called Kolar Gold Fields Limited. They used coir mats. I had training in this company for one month. They had age old stamp mills and tables to separate gold powder. I have innovated one New air separator for iron ores . It may work for gold also. Kindly send me your paper on this subject---- to my e mail ID kshir.saiteja@gmail.com

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  2. Dear Thomas,
    I have just read your paper "Selective attachment processes in ancient gold ore beneficiation" published in Minerals Engineering. This is a fascinating paper and I am very pleased to see that Minerals Engineering has published it.

    I work extensively on gold phytomining and totally agree with your commentary that we are perhaps only "rediscovering" what was known before.

    I was hoping you would be able to give me a little more background on what compelled you to write this paper. Are you a historian?

    Respectful yours,
    Chris Anderson, Massey University, New Zealand

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    1. Dear Chris!
      Thank you for your kind comments on my paper. The chapter on phytomining was a complicated part indeed. Therefore, I am glad that you agree with me on this particular issue. Your papers were very helpful in this respect.
      On my background the following: I studied Mineral Processing at the Bergakademie Freiberg/Germany. From 1992-2005 I was professor and chair of the Department for Environmental Processs Engineering at the University Erlangen/Nuernberg in Germany. Since my retirement I am interested in mining history. Actually, the paper was a "bypyproduct" of a project that focused on relics of prehistoric gold washing here in Germany. Colleagues were very skeptical due to the very low gold contents of gold sand. The assumption expressed already in the past, that the ancient beneficiation art was on a higher level than previously anticipated, was the incentive for my research and this review article. By the way, even in density sorting, we found some intriguing details unknown and unpublished as of now.
      I wish you further success in your research that I will pursue with great interest.
      Best wishes
      Thomas

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