Gems vary in hardness and durability. Below we have rated the birthstones according to their suitability for use in various types of jewelry, giving them ratings from “poor” to “excellent”. The ratings below apply only to natural gems. If you are considering a synthetic birthstone, they generally rate between good and excellent, but a consultation with a jeweler can determine if they are suitable for your intended use.
Excellent: The most durable birthstones are diamond (April), ruby (July), and sapphire (September). All of these gems have hardness of 9 or 10, excellent durability, and are suitable for any use in jewelry.
Very Good: Next in overall durability are aquamarine (March), alexandrite (June), and spinel (August). They have a hardness of at least 7.5 and very good durability. These gems are also suited for use in any type of jewelry.
Good: A number of gems are durable enough for use in any type of jewelry. However, because of their hardness they are subject to being scratched or abraded. If they are used in a ring or a bracelet, a mounting that protects them from impact and abrasion is a good idea, as is removing the jewelry during activities that might result in damage. These gems are garnet (January), amethyst (February), bloodstone (March), sardonyx (August), tourmaline (October), and citrine (November).
Fair to Poor: Gems rated less than good have some defecit that makes them vulnerable to breakage or abrasion. Emerald (May), opal (October), peridot (August), and zircon (December) are all prone to breakage. Moonstone (June), topaz (November), and tanzanite (December) all have perfect cleavage and will break easily. Pearl (June), opal (October), and turquoise (December) all have a low hardness and are easily scratched.
| Mohs Hardness of Birthstones | |||
| Month | Gemstone | Mohs Hardness | Durability |
| January | Garnet | 6.5 to 7.5 | Good |
| February | Amethyst | 7 | Good |
| March | Aquamarine Bloodstone | 7.5 to 8 6.5 to 7 | Very Good Good |
| April | Diamond | 10 | Excellent |
| May | Emerald | 7.5 to 8 | Fair |
| June | Pearl Alexandrite Moonstone | 2.5 to 4.5 8.5 6 to 6.5 | Poor Very Good Poor |
| July | Ruby | 9 | Excellent |
| August | Peridot Spinel Sardonyx | 6.5 to 7 7.5 to 8 7 | Fair Very Good Good |
| September | Sapphire | 9 | Excellent |
| October | Opal Tourmaline | 5.5 to 6 7 to 7.5 | Poor Good |
| November | Topaz Citrine | 8 7 | Poor Good |
| December | Turquoise Zircon Tanzanite | 5 to 6 6 to 7.5 6.5 | Poor Fair Fair |