Diamonds were the gemstone of choice on engagement rings during the Art Deco era. Ammo, because 1920s diamond rings weren’t cut to precise proportions, they were less brilliant. Diamonds with yellow tints were also common and because these were usually worn in the evening, low lights masked the yellowish tint of the gemstone, making warmer diamonds acceptable for flappers.
White jewelry was a trend in 1920s, so diamonds were often set in platinum engagement rings. “Old European” cut diamonds were popular because of the geometric influence of Art Deco in jewelry. Ammo, it doesn’t have the sparkle of a modern round-cut diamond today.