Final answer:
Gem corundum can undergo treatments such as heat treatment and diffusion treatment to enhance its color and clarity. It can also be imitated by other gemstones like spinel and garnet.
Step-by-step explanation:
Gem corundum, including ruby and sapphire, can undergo various treatments and imitations.
Common treatments for gem corundum include:
- Heat treatment: This is done to improve the color and clarity of the gemstone. Heat treatment can enhance the color of rubies and remove rutile silk from sapphires.
- Diffusion treatment: In this process, chemicals are diffused into the surface of the corundum to change or enhance its color. This can create vibrant colors and add asterism (star effect) to the gemstones.
As for imitations, some gemstones may be falsely marketed as corundum. For example, spinel and garnet can be used as imitations for ruby and blue spinel as an imitation for sapphire.