The mineral corundum produces sapphires of every color of the rainbow, including red ones, which are known as rubies. When polished and cut, rubies can be among the largest and most costly of gemstones. However, before they go through the cutting process, rubies can be much more unassuming. When taken straight from the ground, rubies may look like nothing more than red rocks.

Rubies tend to grow in a roughly hexagonal shape. Typically, the surface of a ruby is flat rather than having the spiky protrusions seen in other crystalline formations. The type of host rock in which a ruby grows may impact its overall shape, with some raw rubies appearing blocky and others adopting a more tapered shape. Although a raw ruby won't have the sheen of a cut and polished stone, rubies in nature will still have a distinctive red hue.