What is corundum with traces of chromium cr?

Corundum with traces of chromium is known as ruby, a precious gemstone characterized by its red color. The presence of chromium ions in the crystal structure of corundum gives it this distinctive hue. Ruby is highly valued in jewelry and is one of the four precious gemstones, alongside sapphire, emerald, and diamond. Its hardness, second only to diamond, makes it a durable choice for various applications.