Jonnagiri in Andhra Pradesh’s Kurnool district is just a village now, but in the days of Ashoka The Great it was the headquarters of the southern part of his empire. Some of his famous 3rd century BCE rock edicts have been found here. You can also see telltale marks of gold prospecting from centuries ago. A huge rockcut well near a temple is probably a relic of an ancient gold rush.
We don’t know how much gold the rocks of Jonnagiri yielded in bygone days. Probably a good deal, for Ashoka made it clear that the gold, gemstones and diamonds found at the site belonged to him. Hundreds of years later, the Cholas were masters of Jonnagiri’s gold. Some more centuries passed, and we know the British tried but weren’t very successful. They moved on to Kolar, about 300km away in Karnataka, and scripted KGF.
Back to golden age
Jonnagiri wasn’t forgotten, though. Thirty years ago, the Geological Survey of India (GSI) came over and looked carefully at the village’s old excavations. Their studies between 1991 and 1994 helped them identify blocks with significant potential for gold extraction.
All they needed to do now was to start picking up the yellow pieces, right? Wrong. Gold is precious because it is so rare. In Jonnagiri, the private mining company Geomysore is prepared to sift through up to 2 tonnes of soil to find 1 gram of gold.
Files had to be moved, government policies made, and it was 2006 by the time Geomysore first applied for a licence to explore Jonnagiri. Clearances didn’t come until 2013. In that time, Facebook had opened to the public, bought Instagram and was on the verge of acquiring Whatsapp. Geomysore – which is jointly owned by Thriveni Earth Movers Pvt Ltd (60%) and Deccan Gold Mines Ltd (40%) – has spent the past 10 years analysing the Jonnagiri site.
“Since the grant of mining lease, we have carried out extensive advanced exploration, which includes trenching, soil sampling, IP survey, magnetic survey and drilling,” says Geomysore’s managing director Dr Modali Hanuma Prasad, adding, “About 33,000 sq metres of close spaced drilling has been done from which we could establish considerable deposits in the area.”
Mining starts next year
Geomysore is gearing up to kick off fullscale commercial operations at Jonnagiri by August 2024, says Prasad, who earlier worked with the GIS. They will be only the second operational gold miner in India after the Karnataka government-owned Hutti Gold Mines Co Ltd, and have set a target of producing about 1 tonne of gold every year through the open pit mining and processing project.
But how much gold does Jonnagiri hold? There’s enough to make the mine profitable, says Geomysore. The gold is distributed across the four blocks – east, west, south and north – of the licence area and detailed evaluation of the east block has shown the presence of 6.8 tonnes of mineable gold. Enough to keep the mine going for 8-9 years.
“The metallurgical test work programme has been conducted primarily at the facilities of SGS Johannesburg, South Africa, with additional evaluation being done at the Indian Bureau of Mines (IBM) facility in Bengaluru,” says Geomysore’s director (operations) Manas Ranjan Biswal.
The company estimates the open pit method will be economically viable till a depth of 180m. They are prepared to mine till the concentration of gold in the ore falls to 0.6 grams per tonne.
“We expect to produce at least 1 tonne of gold annually, which could bring the firm into break-even range within 5-6 years,” says Prasad, adding, the detailed assessment of the west, north and south blocks could potentially increase the mineable gold to 14 tonnes, and the mine life to 15 years.
Moving mountains of ore
Luckily, gold in the Jonnagiri ore can be recovered with the cheap ‘gravity separation’ method, says Biswal. To achieve the target of 1 tonne per annum of gold, a processing plant with a capacity to sift through 1,500 tonnes of ore daily will be set up.
The ore will be crushed in three stages and then pulverised in a ball mill before the gold is separated from the dirt in a hydrocyclone, a kind of centrifuge. The machine will churn 50 tonnes of ore per hour.
For now, though, a pilot-scale processing plant based on the gravity technique is being used. This plant has a capacity of 2 tonnes per hour and it has helped the company understand the commercial and technical aspects, and minimise risks.
Geomysore has already spent Rs 200 crore on the project and will invest more when starting commercial operations.