An old mine diamond is a type of antique diamond cut that was most popular from the early 18th century to the late 19th century. It is characterized by a squarish shape with rounded corners, a smaller table facet, a higher crown, a deeper pavilion, and a large culet, with generally 58 facets. It was hand-cut, often leading to unique and slightly asymmetrical stones. This cut was designed to maximize brilliance under candlelight, creating a distinctive sparkle with larger, rougher-cut facets compared to modern diamonds. The old mine cut is considered a precursor to the modern cushion cut diamond and has a softer, more diffused glow compared to modern cuts.