Raghav Gadgil
Some people like to measure their financial might by the weight of the precious metals they wear as jewellery: Gold, silver, diamond and platinum. Gemstones are clubbed with these to bring good fortune. However, few have an inkling of how these metals are extracted or where they form. These metals/minerals hold a giant back-story of geology and human muscle.
Gold is a heavy metal; most of it has been gravity-settled in the molten earth since the earliest times. It forms when hot water races through rock fractures, leaving hair-thin metal threads. Due to weathering and erosion, residual gold can accumulate in the river bed. A 6-gram anniversary gold ring on the finger requires grinding and pulverisation of 20 tonnes of rock. The open pit mines, like the iron ore mines we have in Goa, use massive trucks whose tire diameter is 13 feet and can carry 450 tons of load (45 times the average mining truck in Goa).
The proverb “Faith can move mountains” may not be true, but mining makes it happen! The most enormous open pit for gold, in Uzbekistan, stretches 3.5 km and plunges 600 m deep—two Eiffel Towers one above the other. India’s Hutti mine (~900m deep underground) in Karnataka is modest by comparison with those in South Africa, which are 4 km deep. At this depth, the air and rock temperature is 60℃, as hot as water dispensed by household geysers. In 2011, through newspaper articles (with annual reminders), it was declared that in Goa, there is ~10 grams of gold/tonne (yes, you heard that right) in laterites and argillites (sedimentary rocks) lying in the plateaus. Independent researchers have not yet confirmed this audacious finding, which amounts to wild speculation.
Apart from occurring as native, silver partners itself with lead, zinc and copper. Mexico and Peru lead global output; in India, the Zawar and other Rajasthan deposits yield silver while targeting zinc and lead. 60 g of silver, almost half the weight of one butter bar, is extracted from 1000 kg of rock. Half of that silver heads into industry: solar panels, circuit boards, and antibacterial medical gear. The rest end up as jewellery or decoration on sweets like Kaju Katli.
The saying “Diamonds are forever” can be taken literally, and they are at least 1 to 3 billion years old. That sparkling diamond in your finger ring formed in the mantle, (200 km below the ground. That's where 1300℃ cooks and ) 63000 times atmospheric pressure squeezes graphite (no, not coal!) to diamond. These diamonds get on as a pillion over the fast-moving kimberlite-type magmas moving through carrot-shaped pipes in the crust. On average, a one-carat gem (about one raindrop) requires 250 tonnes of dirt and rock to clean. Until the eighteenth century, India supplied diamonds to the world, but today, it is taken over by Russia and Botswana. Not all diamonds end up as jewellery; some end up as abrasives, as it is the naturally occurring hardest substance.
Platinum is the rarest. It gathers in thin, centimetre-thick layers inside ancient magma chambers, today found abundantly at Merensky, South Africa. Miners there descend more than 2 km underground to follow layers thinner than a dining table top. An amount of rock weighing slightly more than four Indian elephants has to be powdered to make a modest 5-gram platinum wedding ring. Global output seldom tops 200T/year, versus over 3000T of gold. Non-economic amounts are found in rocks at Bondla-Usgao, Goa.
After learning this, I hope you will look at a piece of jewellery or a shiny coin differently. These items are not just symbols of wealth or beauty – they are also symbols of the colossal undertaking that mining industries and their workers perform, and of the environmental trade-offs society makes to enjoy these materials. Remember the incredible journey from the bowels of the Earth to your hand. Knowing all this sharpens our sense of value and perhaps our respect for the extraordinary geological and human work that brings these treasures to light.