What is an Old Mine Cut Diamond?

Before laser cutting or precision tools revolutionized the diamond industry, these gems were cut by hand using bow-driven wheels and rudimentary polishing tools that would seem primitive by today's standards. The process began with careful examination of the rough stone, as cutters had to work with the diamond's natural crystal structure without the benefit of computer modeling or advanced planning tools. Cutters relied entirely on visual balance and years of apprenticeship-honed instinct rather than strict mathematical angles, so the results were unique to each stone and reflected the individual artisan's style.

The cutting process for Mine Cut diamonds involved multiple stages of increasingly fine abrasion. First, the rough diamond would be cleaved along its natural grain using a sharp blow with another diamond—a nerve-wracking process where one mistake could shatter the entire stone. Next came bruting, where two diamonds were rubbed together to create the basic rounded square shape. The faceting stage used a cast-iron wheel charged with diamond dust and oil, with the cutter holding the stone by hand or in a primitive dop stick, carefully grinding each facet while constantly checking proportions by eye.

The goal wasn't brightness under showroom lights—it was fire and glow under the flickering flames of candles and gas lamps. That's why Old Mine Cuts have deeper proportions and higher crowns, helping light bounce within the stone to create broader flashes of color even in low light conditions. The large open culet wasn't just a stylistic choice—it was often the result of practical cutting constraints and the belief that a pointed culet would be more prone to chipping. These diamonds were cut to maximize carat weight retention from the rough stone, often resulting in shapes that followed the natural octahedral form of diamond crystals rather than forcing them into predetermined proportions.

These antique diamonds technically have the same number of facets as a modern round brilliant—58—but that's where the similarity ends. The arrangement and proportions of these facets create an entirely different visual effect. Old Mine Cuts tend to have chunkier, more uneven facets, especially around the pavilion, where modern cuts would feature precisely angled lower girdle facets. You'll also notice a smaller table (typically 40-50% of the diameter compared to 53-58% in modern cuts) and a more prominent crown that can be 15-20% of the total depth.

The facet pattern of Mine Cut diamonds follows what's known as the "old brilliant" style, with triangular and kite-shaped facets arranged in a less systematic pattern than modern cuts. The star facets on the crown are often irregular in size, and the pavilion main facets may not align perfectly with their crown counterparts. This misalignment, far from being a flaw, creates the characteristic "chunky" light return that collectors prize—broad flashes of light rather than the countless tiny sparkles of modern diamonds.

That large culet at the center of the pavilion can often be seen straight through the table like a window, a dead giveaway that you're looking at an antique. In Mine Cut diamonds, this culet can be up to 10% of the table's diameter, creating what some describe as a "hole" in the center of the stone when viewed face-up. It's this irregular facet layout, combined with the steeper crown and pavilion angles, that gives the stones their mellow, flickering sparkle—a romantic glow rather than the bright, crisp flashes of modern cuts. The light performance prioritizes fire (colored light dispersion) over brilliance (white light return), making these diamonds particularly enchanting in intimate lighting conditions.

These diamonds offer something you just can't get from mass-produced stones: undeniable personality and historical authenticity. Because each one was cut by hand over the course of days or even weeks, no two are exactly alike. The slight variations in facet size, the unique proportions chosen by the craftsmen, and the wear patterns accumulated over centuries of use create a fingerprint-like individuality. That irregularity is part of their charm—collectors and jewelry lovers see it as character, not flaw, appreciating the human touch evident in every facet.

The cultural cache of Mine Cut diamonds extends beyond mere rarity. They represent a tangible connection to history, having potentially adorned the fingers of Victorian ladies, survived through world wars, and witnessed centuries of human drama. Modern buyers are increasingly drawn to the sustainability aspect as well—choosing an antique diamond means no new mining, making it an environmentally conscious choice. The stones also offer exceptional value in many cases, as they're often priced lower per carat than modern cuts despite their scarcity, though particularly fine examples command premium prices.

Old Mine Cuts are also becoming increasingly rare in the market. Since they're no longer being made and many have been recut into modern shapes over the decades to increase their brilliance, the remaining supply continues to dwindle. This scarcity drives demand, especially when pop culture moments thrust them into the spotlight. Swift's ring might've introduced the style to a new audience, but it's longtime collectors who've kept interest alive for decades, carefully preserving these gems from being recut and lost to history. Auction houses report steadily increasing prices for quality examples, and jewelers specializing in antique stones often have waiting lists for specific sizes and qualities.

Start by examining the overall shape: most Old Mine Cuts are cushiony squares with rounded corners, though the exact proportions can vary from nearly round to distinctly rectangular. The outline often appears slightly irregular when compared to the laser-precise symmetry of modern cushion cuts. From the side profile, you'll notice a taller crown (the top portion above the girdle) and a deeper pavilion (the bottom portion) than contemporary cuts—the crown angle typically ranges from 35-40 degrees compared to 34.5 degrees in modern stones.

When viewed face-up, several distinguishing features become apparent. The table looks noticeably smaller than on modern diamonds, often appearing as a distinct geometric window surrounded by the angled crown facets. The culet—that round or octagonal facet at the bottom—will be clearly visible through the center of the table, sometimes appearing as a dark circle or window depending on the lighting. Look for the characteristic "kozibe effect"—a ring of light that appears to circle within the stone when it's rocked back and forth, created by the specific angle relationships between the crown and pavilion facets.

Because they were cut by eye rather than machine, facet symmetry isn't perfect—and that's actually one of the most reliable indicators of authenticity. Use a 10x loupe to examine the girdle, which in Mine Cut diamonds is often bruted (frosted) rather than polished, and may show an uneven thickness. The facet junctions won't meet at precise points, and you might notice slight variations in facet size even on opposite sides of the stone. If you're unsure whether a stone is truly antique, a trusted jeweler can confirm by checking the proportions against known parameters for Old Mine Cuts and looking for telltale wear patterns like tiny chips along facet edges that have been smoothed by decades of wear. Some gemological laboratories now offer reports specifically for antique cuts, documenting their unique characteristics without penalizing them for traits that would be considered flaws in modern stones.