Creative processes in Nature rarely yield what we consider to be perfection. Most natural gemstones contain flaws, called inclusions, that interfere with the clarity of the gemstone crystal. That interference obstructs the passage of light, to some lesser or greater extent, through the gem.

Inclusions are very small fractures in the crystal structures of the gem. Inclusions can appear as specks or they can make a gemstone appear opaque. Light that might be reflected through the gemstone crystal is limited by the greater extent of inclusions and the stone therefor appears less bright.

Most gemstones are opaque to some extent or another. Naturally flawless or near flawless stones are extremely rare and therefore tend to be very valuable.

Sapphires tend to be less included than emeralds and rubies. Because their crystal also tends to be softer and more brittle than rubies and sapphires, emeralds should normally be considered fragile. With deep inclusions, emeralds can suffer easy breakage from trauma and even temperature changes.