| Gemstone | Treatment Method | Special Care & Advice |
| Amethyst | Almost always heated to improve appearance or deepen color. | Clean with warm soapy water and a soft brush or cloth. Do not expose to intense heat. |
| Aquamarine | Usually heated to improve appearance | Clean with warm soapy water and a soft brush or cloth. |
| Black Diamond | There are two different processes that create black diamonds: heat treatment and irradiation. Heat treatment exposes the diamond to high temperatures, which creates graphite residue in the crystal. Irradiation modifies the crystal structure of the stone. | None |
| Blue Topaz | Usually irradiated and heated to produce color. Some topaz may be coated to produce color. | Clean with warm soapy water and a soft brush or cloth. |
| Citrine | Usually heated to improve appearance. | Clean with warm soapy water and a soft brush or cloth. Do not expose to intense heat. |
| Coral | Usually dyed or bleached to enhance color. Sometimes stabilized with colorless plastic to increase durability and to improve appearance. Sometimes stabilized and compressed under extreme pressure and heat to bind together small pieces of natural material into a larger whole. | None |
| Cultured Pearl | Usually bleached and polished to achieve uniform color and shape. May be dyed or irradiated to produce various colors. | Clean with a soft cloth. Do not use ultrasonic cleaner or steamer. Avoid contact with cosmetics, hair spray, perfume, and household chemicals. |
| Emerald | Usually penetrated with oil, wax, or resin to improve appearance. Occasionally dyed with color agents. | Clean with a soft cloth. Do not use ultrasonic cleaner or steamer. Avoid contact with cosmetics, hair spray, perfume, and household chemicals. |
| Garnet | None | Clean with warm soapy water and a soft brush or cloth. |
| Lapis Lazuli | Usually penetrated with oil, wax, or resin to improve appearance. Occasionally dyed. | Clean with a soft cloth. Do not use ultrasonic cleaner or steamer. Avoid contact with cosmetics, hair spray, perfume, and household chemicals. |
| Ruby | Surface cavities and fractures are filled with glass and glass-like substances that contain lead. Usually heated to improve appearance, and sometimes diffused to enhance color. | Clean with warm soapy water and a soft brush or cloth. Avoid strong detergents, heat, pressure, and ultrasonic cleaners and steamers. Avoid re-polishing or re-cutting of the stone. Color may fade in light or with heat. |
| Morganite | Commonly heat treated to enhance color | Clean with warm soapy water and a soft brush or cloth. |
| Mother-of-Pearl | Usually bleaced, dyed, irradiated, and/or coated to enhance color. | Clean with warm soapy water and a soft brush or cloth. |
| Onyx (Black Chalcedony) | Always dyed. | Avoid exposure to extreme light and heat as stones may fade. |
| Opal | None | Clean with a soft cloth. Do not use ultrasonic cleaner or steamer. Avoid contact with cosmetics, hair spray, perfume, and household chemicals. |
| Peridot | None | Do not use ultrasonic cleaner or steamer. Avoid sudden temperature changes and contact with harsh chemicals. |
| Quartz (Rose, Smoky, and Lemon) | Usually dyed or bleached to enhance color. Sometimes surface enhanced with a coating to enhance color. | Avoid abrasives, harsh chemicals, steam and ultrasonic cleaning. Clean with warm soapy water and a soft brush or cloth. |
| Ruby | Usually heated to enhance color. Heat treatment exposes the ruby to high temperatures, which creates moderate or minor residue that collects in feathers in the stone. | None |
| Sapphire | Usually heated to improve appearance. Occasionally irradiated. Commonly diffused along with heat application to create different colors. Yellow sapphire is always diffused. | Clean with a soft cloth. Do not use ultrasonic cleaner or steamer. Avoid contact with cosmetics, hair spray, perfume, and household chemicals. Avoid re-polishing or re-cutting of the stone. Color may fade in light or with heat. |
| Tanzanite | Usually heated to improve appearance. | Clean with warm soapy water and a soft brush or cloth. Do not expose to intense heat. |
| Tourmaline (Pink & Green) | Commonly heat treated to improve appearance. | Clean with warm soapy water and a soft brush or cloth. Do not expose to intense heat. |
| Turquoise | Commonly treated or impregnated with plastic, wax, or colorless oil. Rarely dyed to improve color. | Clean with warm soapy water and a soft brush or cloth. Do not expose to intense heat. |
| Manufactured Turquoise | Usually stabilized with plastic to enhance durability. Dyed to enhance color. | Clean with warm soapy water and a soft brush or cloth. Do not expose to intense heat. |