In modern times, diamond-tipped tools, such as drill bits, burrs and saw blades, are used to carve and shape gemstones due to their exceptional hardness and ability to cut through just about any material.
But, did you know that ancient jewelers knew that secret more than 2,000 years ago?
According to a new study published in the journal Archaeological and Anthropological Sciences, the ancient nomadic tribes that traversed Central Asia used diamond drills to perforate gemstones when crafting necklaces, bracelets and pendants.
The researchers employed Scanning Electron Microscopy (SEM) to study the interior drill hole surface of 51 stone beads recovered from the ancient Rabat Cemetery in Uzbekistan. All of the bead varieties — including carnelian, agate, and garnet — rated a 6.5 to 7 on the Mohs hardness scale. Diamond, by comparison, carries a Mohs rating of 10 and is the hardest naturally occurring material known to man.
The burial site, in the historic region of Bactria (encompassing parts of modern-day Afghanistan, Uzbekistan and Tajikistan) was used by the nomadic Yuezhi people from the second century BC to the first century AD.
Of the 51 beads studied, 41 presented markings associated with the use of a diamond drill. The researchers noted that the Yuezhi used two distinctive types of diamond drills to perforate gemstones. The ancient jewelers used a single diamond drill to start the hole, and then switched to “a narrower double diamond drill with two symmetrically placed diamonds at the tip of the drill” to finish their work.
There was also evidence that the artisans drilled holes from both sides of the same bead, with the holes converging in the middle.
The researchers pointed out that there are significant differences between the diamond drilling techniques used in Bactria and those seen on similar beads from the Indus Valley (modern-day Pakistan, northwest India and northeast Afghanistan). This finding suggests that the drilled beads were manufactured locally and not imported from the Indus region.
Other ancient civilizations successfully drilled holes in gemstones without the assistance of diamonds. Instead they used a combination of tools and abrasives, including copper tubes, sand and possibly other materials, such as quartz or corundum, often with the aid of a bow drill or similar rotating mechanisms.
Credit: AI-generated gem market image by The Jeweler Blog using ChatGPT and DALL-E 3.