Ancient Indians had knowledge about several precious metals and gems. They created mines to extract these precious metals. Here is how precious metals and gems were discovered in ancient India –
Colors resembling the fruit of jambu, mango, palm fruit, arsenic, honey, feathers of a parrot or a peacock, and vermilion, etc., were supposed to be indicators of gold mines.
If any liquid found under the rock, after pouring into water, spread like oil and absorbed the mud and dirt, it indicated copper or silver ore.
The akaradhyaksha, official in charge of mines in ancient Hindu kingdoms, had technical knowledge, which included the following according to Arthashastra –
Yellow or reddish-yellow rocks, if they showed blue lines when broken, indicated copper and silver ores.
Rocks with the color of the conch shell, camphor, crystals, butter, and a peacock’s neck indicated lead.
Rocks of similar color but smelling like raw fish were the indicators of silver.
Presence of ore was indicated by the heaviness of pebbles or stones.
Saline and grey rocks yielded tin metal.
Lustrous, smooth, cold, and hard rocks producing a tinkling sound when tapped were the ores of gems.
The head of the metallurgical department tested the viscosity of the ore by pouring hone or liquor on the ore, which made it soft.