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Sunday, January 23, 2022

Know Your City: Cavansite, a rare turquoise-hued mineral unique to Pune

“If you go to any museum in the world and they have Cavansite, it has to be from Pune. It is a greatly prized mineral because it is so rare,” says Muhammad Fasihuddin Makki, a city-based mineral collector.

Written by Dipanita Nath | Pune |
Updated: December 12, 2021 7:49:28 am
Cavensite, found in Wagholi, Pune, in 1998, from the collection of MF Makki.

When Pune-based blogger Ranjit Ghatge visited the Natural History Museum in London, he was surprised to see a magnificent turquoise-coloured crystalline rock in a glass display case at the entrance, with a plaque that said, ‘Beautiful Cavansite from Wagholi quarry of Pune, India’. “The stone attracted my attention. Although I was born and raised in Pune, I did not know that a rare stone is found in the city,” says Ghatge whose blog is called Pune Memories.

Pune is considered to be the only place in the world where Cavansite is found in relatively large quantities. Other quarries in the US, Brazil and New Zealand have yielded only small amounts of the mineral. In Pune, it is found at Wagholi, about 25 km east of the city on the Pune-Ahmednagar Road. “If you go to any museum in the world and they have Cavansite, it has to be from Pune. It is a greatly prized mineral because it is so rare,” says Muhammad Fasihuddin Makki, a mineral collector based in the city. There are lots of colourful, crystalline minerals in the showcase where Makki keeps his collection from around the world, but a deep-blue piece tells the story of a Pune that is millions of years old.

Cavansite is a mineral which formed in igneous rock when molten lava, water, steam and various chemicals were in circulation. “Mineral-rich fluids filled cavities and, over a period, crystallisation of minerals took place due to hydrothermal action,” says Makki. The metal vanadium was brought to the surface from the earth’s mantle by lava flows in the Deccan Traps and, in Pune, it crystallised with silica and calcium to form Cavansite.

The discovery of the mineral’s presence in Pune in 1988, begins with a miner, who was working in a quarry at Wagholi and saw pieces of radiant blue minerals among the stones. He contacted geologist Arvind Bhale who had a penchant for travelling across India collecting minerals.

M F Makki with Scolecite specimen from Junnar Quarry in 2006. (Pic Courtesy MF Makki)

“In the 1970s and ’80s, it was not well-known among people that minerals were used in universities, museums and as collectibles. When Arvind saw this new mineral, he was surprised. A geologist from Australia mentioned that this kind of mineral was found in Utah in the US. With his chisel and hammer, Arvind took some samples and sent these to Germany because at that time India did not have adequate facilities to study mineral refractive index and other details, and the mineral was identified,” says Jyoti Bhale, the late geologist’s wife.

The owner of the quarry turned out to be Bhale’s school friend who allowed him to extract the mineral, which was not an easy job. “In Wagholi, Cavansite was found in large quantities between 1989 and 1995, and people from geology circles the world over were astonished. Lots of researchers and collectors visited Wagholi. Arvind published a number of papers and is known in the mineral world as the Cavansite man,” says Jyoti.

Dr Arvind Bhale with a Cavansite specimen in Wagholi quarry in 1989. (Pic courtesy Jyoti Bhale)

At the Savitribai Phule Pune University, the Geology Department has placed a specimen of Cavansite as the centrepiece of its collection. In lectures to students, Associate Professor of Geology Raymond Duraiswami introduces it as a mineral that has “tremendous potential in material science and for futuristic application and industrial use”. “Cavansite belongs to a group called zeolites, minerals with a large cavity in its molecular structure. Since there is a metal (vanadium) in Cavansite, it is free to exchange cations or an electron with other substances. For instance, if you pass vehicular exhaust through a metal (vanadium)-based zeolite, any lead, cadmium, arsenic or toxic gases in the exhaust will be trapped. So the mineral serves as a micro-filter and a catalytic converter,” says Duraiswami.

The quarries in Pune and its surrounding areas in Maharashtra are rich in several minerals such as Green Apophyllite and Mesolite. “When the railway line from Bombay to Pune was being constructed in the early part of the last century, the workers encountered the ghat section and had to bore a tunnel at Khandala ghat. In one of the tunnels, they found a cavity full of sparkling minerals, like diamonds. Everybody was excited because they thought they had found a big cache of diamonds. The news spread and people started to flock to see this tunnel. They did not know that these were White Apophyllite. The railways had to seal the area to prevent people from obstructing their work, but before sealing they took out the mineral, most of which went to England,” says Makki, whose father started collecting minerals as a hobby in the 1940s when he moved from Karnataka to Maharashtra.

Green Apophyllite from Pashan Quarry 1978 (Pic Courtesy MF Makki)

Today, Makki’s minerals and fossils collection, which he exhibits for free at schools, colleges and other institutions across India to popularise geo science, enables students and others to experience the wonders of nature. “Unlike other exhibitions, I allow and encourage students and visitors to touch the exhibited minerals,” he says. Visitors can hold the Green Apophyllite, the needle-like crystals of Mesolite, and the specimens of Cavansite and rare minerals from India and around the world. “It gave me goosebumps to find cavities full of minerals. Unfortunately, mines have closed down around Pune, such as in Erandwana quarry, Pashan Hills, Chinchwad and Wagholi as strict town planning regulations, environmental curbs and rapid urbanisation have forced quarry owners to shift to faraway areas where land is cheap. Quarry zones of Wagholi have turned into valuable real estate areas and are now engulfed by construction activities,” says Makki.

Duraiswami says that not a lot of research has gone into understanding the structure or genesis of Cavansite. “While we can use it in catalytic converters and so on, the characterisation of Cavansite is still going on. Since this mineral has industrial and other applications, a lot of people will also not share their research. We at Savitribai Phule Pune University are now characterising this spectacular blue mineral using state-of-the-art mineral technology at central instrumentation facilities set up for the purpose,” he adds. Now that the mines are closed, no new Cavansite specimens are coming out and any commercial material sold today is from previous stock.

“There is a need for awareness about this mineral. We have national and state animals, birds and plants, but if there is a mineral for Maharashtra or a national mineral, it should be Cavansite. It is a treasure trove yet to be explored,” says Duraiswami.

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