In 1947, the Linde Air Products Company of New York began producing a form of synthetic gem corundum that was marketed in the gemstone industry as "Linde Star Sapphire." Also called Lindy stars, these laboratory-created gemstones were known for the perfection of their asterism, showing as a 6-pointed star under normal lighting. The Linde stars were sold as round and oval cabochons in various sizes and colors. Production of the Linde stars was discontinued in 1974 due to foreign competition. The example shown here is a pink, oval, Linde star measuring 12 x 10 x 6 mm. It shows intense, saturated, red fluorescence under long wave UV.
The upper image shows the Linde star under normal, visible light conditions. Note the well-defined six-pointed star. The lower image shows the intense red fluorescent response under long wave UV (365 nm).