The Dutch master Vermeer was famous for his Girl with a Pearl Earring. In South India I am convinced he would have been pressed upon to depict “Lady With a Diamond Nose-stud.”

The middle-aged couple ar rived at the famous doctor’s clinic in their Rolls Royce. With her check-patterned silk saree, ruby earrings, and chunky gold bangles, the woman seemed dressed for a wedding reception, but she was really there for a consultation. Her medical complaint: Every afternoon, she took her tea outdoors in the garden of her large home but, lately, she had been coming down with severe headaches soon after. “I can cure you,” said the doctor, “but it’ll cost you your new nose stud.” That was a peculiar fee he was asking for.

Much like the physician Sherlock Holmes was modelled after, the doctor, owner of a Silver Ghost himself, paid attention to the tiniest of details about patients who walked in through his door – their gait, their clothes, even the colour of the mud under their shoes – all in the cause of good diagnosis. So, he’d noticed the woman’s nose-stud, which consisted of a single stone, with five diminutive diamonds around its base. When sunlight fell on the central diamond, it became suffused with a bluish glow. The intensity of that glow, he suspected, caused her noontime agony. Diagnosis done, he proceeded with the ‘cure’. For the record, he took cash for the treatment; the couple’s gratitude was a bonus.

This apocryphal story is the stuff of Madras medical school legend, but there is nothing mythical about these exquisite diamonds. Blue jagers, prized in South India, originated in South Africa, where diamonds were discovered for the first time in 1867. The bluish-white diamonds were unearthed at the Jagersfontein mine. Jewellers prefer colourless diamonds, but they made an exception for blue jagers, which are essentially white but can emit a distinctly bluish glow.

Photochemistry has a simple explanation for that blue glow: fluorescence. A fluorescent substance can absorb at a certain wavelength and emit at another. Some diamonds, because of the impurities in their crystal lattice, absorb invisible ultraviolet rays from intense sunlight or a special lamp, and emit blue light, which the human eye can see. Such rare bluish-white diamonds fetched a premium. The jager rating once went to the very best diamonds, but it soon became an obsolete term.

In the second half of the 20th Century, the international community of jewellers drew up a list of criteria to evaluate the quality of a diamond. Thereafter, the gem’s colour, cut, clarity and carat weight would determine its price. Diamond fluorescence tends to be less regarded, but these things can be a matter of individual taste. The Jagersfontein diamond mine closed operations in 1971. Nostalgia, however, is a powerful thing and old connoisseurs continue to speak of blue jagers. And you’ll, of course, find the occasional references to them in old books and magazines.

In the delightful biography, R. K. Narayan, The Early Years, you read about the novelist’s mother Gnana. “She would look resplendent in her nine-yard sari, her earrings, seven Blue Jager diamonds set in each, and her single-diamond nose-stud,” says her granddaughter Hema. In this attire, Gnana played tennis or sat down for a game of chess and bridge at the Ladies’ Club. Her partner was the Maharani of Mysore, to whom she diplomatically lost on many an occasion. This won her invitations to play at the palace and, as the evening drew on, Gnana would return to her anxious family in the royal Rolls Royce. Palace servants followed, bearing gifts of sweets and nuts. With these treats, and by her lively narration of the events of the day, she would dispel the tension at home. Along with her sparkling diamonds, luckily she also had a sparkling wit.

Another woman who was very much in the public eye owned a pair of these blue jager earrings. Carnatic singer M.S. Subbulakshmi used to lay out these special studs carefully along with her saree, blouse, and other accessories by 2.30 p.m. on concert days, according to an article in Sruti magazine. M.S., as she was popularly known, favoured a certain deep shade of blue for her silk sarees, which a silk merchant and music aficionado created specially for her. Her female fans began clamouring for “M.S. Blue” sarees. Some bought blue jager earrings as well. The singer might’ve never thought of herself a style icon but, to this day, many older South Indian women aspire for her aesthetics in appearance.

Truth is that women in our part of the world have long relied on sparkling stones to lend them radiance after the glow of youth is gone. Blue jagers and white diamonds are meant to dazzle the beholder. A pair of earrings, set in the classical seven-stone design, often does just that, as do diamond-encrusted nose studs. Sometimes, of course, the plan backfires, as it did for the poor woman who suffered from the stone’s radiance. But it must have been a simple matter for her to direct the Rolls Royce to a jeweller’s shop, ask him to find the diamond’s twin, and have them set in a flattering new design – a pair of earrings, maybe. Then, she would’ve proceeded to enjoy the gleeful brilliance of the stones in accordance with tradition.