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Line 170: − + − + − + + + − + + + + + + + + + + + + + + + + + − === रजतः ॥ Silver ===+ − Unlike gold, the brilliant white metal silver, is related to Chandra, has been introduced relatively late largely because of its non-availability in the nature as native metal. It is rarely found in nature as virgin metal. + + + + + + + + + + + + + + + + + + + + + + + + + Line 211:
Line 253: − − === सीसम् ॥ Lead === − The Harappans were acquainted with lead ores such as galena (Lead sulphide) and cerussite (carbonate), and their smelting process which is simple on account of easy reducibility and low melting point of the metal. Lead was commonly alloyed with copper and bronze for making castings. The mineral-rich Aravalli region of Rajasthan was one of the important early lead mining regions in antiquity. − * Lead was used in making alloys.
adding content and references
== The Eight Metals of Antiquity ==
== The Eight Metals of Antiquity ==
The present section reviews the important metals and interesting points about their role since ancient times.
The present section reviews the important metals, their qualities, ores and interesting points about their role since ancient times. One of the ancient texts that gives a comprehensive view about metals is Kautilya's Arthashastra. Though a book on polity and administration, it gives a great deal of information regarding many aspects of life such as agriculture, economy, trade, metals and gems, occupations, weapons and spies and many other interesting out of the norm situations. A summary of the description of the ores, management of mines, rock veins of minerals, metals (gold silver copper and their alloys) with their extraction and working, as well as of alloys, information of fabrication of metallic artefacts are found in the text. Kautilya outlines the duties of the Superintendent of Mines (लोहाध्यक्षः) and gives him the details of the ores of metals and their fabrications in Adhyaya 12 of Adhikarana 2. Some common observations about the ores are also mentioned by Kautilya such as <blockquote>सर्व-धातूनां गौरव-वृद्धौ सत्त्व-वृद्धिः ।। ०२.१२.०७ ।। (Arth. Shast. 2.12.7)<ref name=":6">Arthashastra by Kautilya ([https://sa.wikisource.org/wiki/%E0%A4%85%E0%A4%B0%E0%A5%8D%E0%A4%A5%E0%A4%B6%E0%A4%BE%E0%A4%B8%E0%A5%8D%E0%A4%A4%E0%A5%8D%E0%A4%B0%E0%A4%AE%E0%A5%8D/%E0%A4%85%E0%A4%A7%E0%A4%BF%E0%A4%95%E0%A4%B0%E0%A4%A3%E0%A4%AE%E0%A5%8D_%E0%A5%A8/%E0%A4%85%E0%A4%A7%E0%A Adhikarana 2 Adhyaya 12])</ref></blockquote>The heavier the ores, greater will be the quantity of metal in them (sattva-vrddhi)
=== सुवर्णम् हिरण्यम् वा ॥ Gold ===
=== सुवर्णम् हिरण्यम् वा ॥ Gold (''Aurum'' - Au) ===
Early reference to gold is to be found in the Rigveda samhita. However, not many gold artifacts dating to Pre-Harappan period have been reported although in Rgveda Gold and its alloys with Ag and Cu have been mentioned in many places, such as, 1-85.9, 88.5, 67.3; II-37.9; V-54.15, 57.1, 60.4; VIII - 7.27-32 etc. In Vedic literature this metal has been mentioned as Hiranya (हिरण्यम्) probably because of its high corrosion and oxidation resistance and the practice of its preservation through generations.<ref name=":5">Bhanu Prakash (1997) ''History of Technology in India, Vol. 1, From Antiquity to c. 1200 A.D. by A. K. Bag.'' New Delhi: Indian National Science Academy. (Chapter Metals and Metallugy: Page 80 )</ref>
Arthashastra describes the qualities of the gold ore thus<blockquote>पीतकास्-ताम्रकास्ताम्र-पीतका वा भूमि-प्रस्तर-धातवो भिन्ना ..... बहुफेनधूमाश्च सुवर्ण-धातवः प्रतीवाप-अर्थास्ताम्ररूप्य-वेधनाः ।। ०२.१२.०५ ।। (Arth. Shast. 2.12.5)<ref name=":6" /></blockquote>''"Those ores which are obtained from plains or slopes of mountains; which are either yellow or as red as copper or reddish yellow; which are disjoined and marked with blue lines; which have the colour of black beans (masha, Phraseolus Radiatus), green beans (mudga, Phraseolus Mungo), and sesamum; which are marked with spots like a drop of curd and resplendent as turmeric, yellow myrobalan, petals of a lotus, acquatic plant, the liver or the spleen; which possess a sandy layer within them and are marked with figures of a circle or a svastika; which contain globular masses (sagulika); and which, when roasted do not split, but emit much foam and smoke are the ores of gold (suvarnadhátavah), and are used to form amalgams with copper or silver (pratívápárthasté stámrarúpyavedharáh)".''<ref name=":7">Shamasastry. R. Kautilya's Arthashastra with English Translation. (Pages 111 - )</ref>
Early reference to gold is to be found in the Rigveda samhita. However, not many gold artifacts dating to Pre-Harappan period have been reported although in Rgveda Gold and its alloys with Ag and Cu have been mentioned in many places, such as, 1-85.9, 88.5, 67.3; II-37.9; V-54.15, 57.1, 60.4; VIII - 7.27-32 etc. In Vedic literature this metal has been mentioned as Hiranya (हिरण्यम्) probably because of its high corrosion and oxidation resistance and the practice of its preservation through generations.<ref name=":5">Bhanu Prakash (1997) ''History of Technology in India, Vol. 1, From Antiquity to c. 1200 A.D. by A. K. Bag.'' New Delhi: Indian National Science Academy. (Chapter Metals and Metallugy: Page 80 )</ref>
A noble metal, gold, is found in the native state, and was used to make jewellery and sheet metal due to the great ductility and lustre of the pure metal. In human civilization it has been named as the most sinister and deadly metal although due to its ductility and softness it had proved worthless for making any war weapon.
A noble metal, gold, is found in the native state, and was used to make jewellery and sheet metal due to the great ductility and lustre of the pure metal. In human civilization it has been named as the most sinister and deadly metal although due to its ductility and softness it had proved worthless for making any war weapon.
Extraction Process: Gravity separation or panning. When a pan containing the suspension is agitated under water, gold particles separate and settle at the bottom of the pan, while sand and soil are washed away. The second process known to ancient craftsmen is that of amalgamation with Mercury and recovery of gold by evaporation and distillation of mercury.<ref name=":5" />
==== Extraction Process ====
* Gold Ore : Native metal associated with silica and soil.
* Gravity separation or panning.
* Amalgamation technique with Mercury
When a pan containing the suspension is agitated under water, gold particles separate and settle at the bottom of the pan, while sand and soil are washed away. This is the simple gravity separation process. The second process known to ancient craftsmen is that of amalgamation with Mercury and recovery of gold by evaporation and distillation of mercury. The technique of Hg amalgamation and gilding was thus well known to the Indian craftmen from the very early times.<ref name=":5" />
In ancient times, gold was collected by panning alluvial sands from placer deposits. However, India has the distinction that the deepest ancient mines in the world for gold come from the Maski region of Karnataka with carbon dates from the middle of the first millennium BC.<ref name=":4" />
In ancient times, gold was collected by panning alluvial sands from placer deposits. However, India has the distinction that the deepest ancient mines in the world for gold come from the Maski region of Karnataka with carbon dates from the middle of the first millennium BC.<ref name=":4" />
* Oldest literary reference to usage of Gold in Rigveda
* Oldest literary reference to usage of Gold in Rigveda
* World's deepest gold mines are found in Karnataka state of India
* World's deepest gold mines are found in Karnataka state of India
* Process of preparing alloys is ancient
=== रजतः ॥ Silver (''Argentum'' - Ag) ===
Arthashastra describes the qualities of the silver ore thus<blockquote>शङ्ख-कर्पूर-स्फटिक-नव-नीत-कपोत-पारावत-विमलक-मयूर-ग्रीवा-वर्णाः ... न स्फुटन्ति बहु-फेन-धूमाश्च रूप्य-धातवः ।। ०२.१२.०६ ।। (Arth. Shast. 2.12.6)<ref name=":6" /></blockquote>''"Those ores which have the colour of a conch-shell, camphor, alum, butter, a pigeon, turtle-dove, Vimalaka (a kind of precious stone), or the neck of a peacock; which are as resplendent as opal (sasyaka), agate (gomédaka), cane-sugar (guda), and granulated sugar (matsyandika) which has the colour of the flower of kovidára (Bauhinia Variegata), of lotus, of patali (Bignonia Suaveolens), of kalaya (a kind of phraseolus), of kshauma (flax), and of atasi (Dinuin Usitatissimum); which may be in combination with lead or iron (anjana); which smell like raw meat, are disjoined gray or blackish white, and are marked with lines or spots; and which, when roasted, do not split, but emit much foam and smoke are silver ores.''"<ref name=":7" />
Unlike gold, the brilliant white metal, silver, has been introduced relatively late in the civilizations largely because of its non-availability in the nature as native metal. It is rarely found in nature as virgin metal and is found associated with lead ores such as galena. A domestic metal, similar to gold, silver has no value in armoury or warfare. Archaeologically, only few silver artifacts have been found dating back to Harappan times, however, the Vedic period has quite some instances of usage of this metal.<ref name=":5" />
==== Extraction Process ====
* Silver Ore : Cerasgerite (AgCl) and Argentite (Ag<sub>2</sub>S) associated with Galena (Lead ore) and/or Sphalerite or mixed sulphide ores.
* Roasting and reduction smelting techniques for the treatment of sulphide
* Purification of Silver by Cupellation.
During the extraction of lead from its ores, Argentite also gets decomposed and reduced easily to readily form an alloy with metallic lead. Pure silver subsequently produced by the process of cupellation. Some scholars mention that these processes were known during the Harappan period. Silver metal is obtained from the alloy of Pb-Ag by reheating it in a shallow hearth furnace having the bottom prepared with bone charcoal. During remelting of the alloy it is subjected to oxidizing condition by blowing excess air when lead gets preferentially oxidized to PbO (litharge) which has a very low melting point. This molten litharge is skimmed off and partially absorbed by the furnace hearth. This process is known as ‘Cupellation'.<ref name=":5" />
The shining white colour, high ductility, high corrosion resistance and the non-tarnishing properties of silver attracted the attention of the primitive men and they found its use in making ornaments, utensils, decorative pieces and other house hold articles. It was popular as a coinage metal in the later periods after the smelting process was well established. Silver has been used in Ayurveda for its medicinal properties.
Interestingly, as far as silver production goes, the Aravalli region in North-West India ranks amongst the few major ancient silver producing sites in the world.
Interestingly, as far as silver production goes, the Aravalli region in North-West India ranks amongst the few major ancient silver producing sites in the world.
=== सीसम् ॥ Lead ===
Arthashastra describes the qualities of the lead ore thus
काक-मोचकः कपोत-रोचना-वर्णः श्वेत-राजि-नद्धो वा विस्रः सीस-धातुः ।। ०२.१२.१३ ।। (Arth. Shast. 2.12.13)<ref name=":6" />
''"Those ores which have the colour of kákamochaka (Solanum Indica), pigeon, or cow‟s bile, and which are marked with white lines and smell like raw meat are the ores of lead."''<ref name=":7" />
The lead artifacts during the Harappan period have been reported showing that the people were acquainted with lead ores (such as galena) and their smelting process which is simple on account of easy reducibility and low melting point of the metal. Like gold and silver, lead did not find extensive usage in tools and implements owing to its softness. It is one of the softest and heaviest metal having shining grey lustre which leaves a black streak on paper.
It is so soft that it can be scratched even with nail hence it’s use has been mostly for the manufacture of cheap jewellery dies or pattern for shaping other metals, and as a hardner in copper alloys.
==== Extraction Process ====
* Lead Ores : Galena (PbS), Litharge (PbO), Cerussite (PbCO<sub>3</sub>)
* Roasting and reduction smelting techniques for the treatment of sulphide
* Preferential Oxidation of lead to PbO (Litharge)
* Removal of pure Silver by Cupellation.
* Reduction of Litharge to produce metallic lead
Since liquid lead readily alloys with silver one of its major use was to first produce this alloy by coreduction of Pb and Ag minerals and then produce pure Silver by the process of cupellation. Litharge which has a low melting point is skimmed off and reduced in an ore hearth furnace to recover metallic lead.
Lead was commonly alloyed with copper and bronze for making die castings. Lead compounds also have been used for glazing potteries and in the manufacture of glass. It was used to prepare Pb-Sn alloy used as solder to join pieces of copper and bronze. In more recent centuries lead has been extensively used for preparing projectiles for slings and catapults, bullets, cannon balls and cast shots etc.
The mineral-rich Aravalli region of Rajasthan was one of the important early lead mining regions in antiquity.
* Lead was used in making alloys of silver, copper
* Chief coinage metal around 1-2nd BCE.
=== ताम्रम् ॥ Copper ===
=== ताम्रम् ॥ Copper ===
* Wootz Steel prepared by indigenous crucible process.
* Wootz Steel prepared by indigenous crucible process.
* Monumental Iron pillars such as the one at Dhar in Central India and Kodachadri in coastal Karnataka and iron beams of the Konark temple.
* Monumental Iron pillars such as the one at Dhar in Central India and Kodachadri in coastal Karnataka and iron beams of the Konark temple.
=== Zinc ===
=== Zinc ===