History, buffed: See how diamonds helped shape Bihar’s Barabar caves

The caves were dedicated by Mauryan emperor Ashoka to the now-extinct religious sect of the Ajivika; Ashoka’s father Bindusara was a patron of the sect.

Stone polished to an almost-reflective smoothness was not unusual in the Mauryan empire (321 BCE to 185 BCE). It’s a skill visible in structures and sculpture from that time. But those works were usually crafted using the soft sandstone; the Barabar caves were carved out of granite, one of the hardest rocks.

So how did they do it? Historian SP Gupta, in The Roots of Indian Art (1980), writes that the Barabar caves were essentially “a sudden technological break with no local history, suggesting the import of these techniques from another culture.” A dominant theory is that the “another culture” was the Achaemenid, of ancient Iran. There are similarities in the finish. Additionally, the capitals of Achaemenid columns and those erected in the Mauryan capital of Pataliputra bear similarities. So do the 3rd-century-BCE Masarh lion unearthed near Pataliputra and the Achaemenid Persian Lion. Clearly there was some cultural exchange occurring between the civilisations.

Some historians have suggested that the same artisans might have been at work, having migrated to India after Alexander the Great sacked the Persian empire in 330 BCE. But even the Achaemenids made their mirror-finish structures and sculpture from sandstone. So the technique for granite had to have come from somewhere else.

There was an ancient culture that buffed granite to a mirror-like shine. It wasn’t the Achaemenid; it was Pharaonic Egypt. The pharaohs used granite extensively, to build pyramids, temples and monuments. In something straight out of an Indiana Jones film, they achieved their mirror-like finish using scrubbers studded with diamond teeth. And the diamonds, came from India.

In Kohinoor (2016), authors William Dalrymple and Anita Anand state: “As early as 2000 BCE, tiny Indian diamonds were being used in polishing and cutting tools in ancient Egypt.” Godehard Lenzen’s 1970 book The History of Diamond Production and the Diamond Trade has more on this.

It is therefore likely that, originally in Egypt and later at the Barabar and nearby caves, tiny diamonds affixed to hand-operated metal or leather scrubbers were used to buff the granite to a shine. There’s another possible Egyptian connection. Carved into the granite just outside the caves are birds that resemble the owl motif from ancient Egyptian temples and sarcophagi. (Owls, incidentally, are not common motifs in Indian temple art.)

The mirror-finish work would continue for a few decades. The Nagarjuni caves adjacent to Barabar, commissioned by Ashoka’s grandson Dasharatha Maurya, also have almost-reflective granite walls. But the practice was then abandoned, never to be revived. There are no mirror-finish walls, for instance, at the grand Ajanta, Karla or Kanheri caves (built in Maharashtra between the 2nd century BCE and 1st century CE) or at the Jain Udayagiri and Khandagiri caves in Odisha (built from the 1st century BCE onwards).

Historians say this was possibly because, while the Barabar and Nagarjuni caves were sponsored directly by the imperial government, the other cave temples were funded largely by businessmen, and they simply couldn’t afford the diamond scrubbers.