Birthstone Guide: Gemstones by Month
The modern birthstone list assigns one or more gemstones to each calendar month. The current standard was first formalized by the American National Retail Jewelers Association in 1912 and has been updated several times since — most recently when tanzanite was added to December in 2002 and spinel to August in 2016. The table below lists modern birthstones by month along with each stone's key physical properties and traditional associations.
For an explanation of what gemstones, crystals, and minerals are as physical objects, see gemstone vs crystal vs mineral. To browse the site's stones by birth month, see the January birth-month page as a starting point for the full birth-month filter series.
Monthly Birthstone Reference Table
| Month | Primary Birthstone | Alternate(s) | Mohs Hardness | Traditional Associations |
|---|---|---|---|---|
| January | Garnet | — | 6.5–7.5 | Calm, health, strength |
| February | Amethyst | — | 7 | Clarity, peace, wisdom |
| March | Aquamarine | Bloodstone | 7.5–8 | Courage, unity, hope |
| April | Diamond | — | 10 | Endurance, purity |
| May | Emerald | — | 7.5–8 | Joy, renewal |
| June | Pearl | Moonstone, Alexandrite | 2.5–4.5 (pearl) | Clarity, balance |
| July | Ruby | — | 9 | Passion, strength, harmony |
| August | Peridot | Spinel, Sardonyx | 6.5–7 | Purity, protection |
| September | Sapphire | — | 9 | Loyalty, wisdom |
| October | Opal | Tourmaline | 5.5–6.5 (opal) | Hope, creativity |
| November | Citrine | Topaz | 7 | Warmth, abundance |
| December | Turquoise | Tanzanite, Zircon | 5–6 (turquoise) | Peace, health |
January: Garnet
Garnet is a group of related silicate minerals, not a single mineral species. Five members are important as gems: pyrope, almandine, spessartine, grossular, and andradite. Common jewelry garnets are iron-bearing almandine or pyrope with a deep red color (Mohs 6.5–7.5); however, garnets occur in nearly every color including orange (spessartine), green (tsavorite grossular and demantoid andradite), and color-change varieties. Garnet is mined in Africa, India, Brazil, and Sri Lanka among many other locations. In tradition, garnet is associated with calm, health, and friendship, and is said by some practitioners to promote clarity and peace of mind.
February: Amethyst
Amethyst is the violet-to-purple variety of quartz (SiO2, Mohs 7). Its color comes from iron atoms that form [FeO4]0 color centers when exposed to natural gamma irradiation over geological time. The color can be destroyed by prolonged UV exposure or heat above roughly 300–400°C. Major sources include Brazil, Uruguay, Zambia, and South Korea. In tradition, amethyst is associated with wisdom, clarity, and calm, and was worn in ancient Greece with the belief it prevented intoxication.
March: Aquamarine
Aquamarine is the blue-to-greenish-blue variety of beryl (Be3Al2Si6O18, Mohs 7.5–8). Its color comes from iron in two oxidation states in the beryl lattice. Crystals can grow large, allowing faceting of substantial gems. The primary source is Brazil; Pakistan, Mozambique, and Madagascar also produce fine material. The alternate March birthstone is bloodstone (dark green chalcedony with red iron-oxide spots). Aquamarine is traditionally associated with courage, unity, and safe travel.
April: Diamond
Diamond is pure carbon crystallized in the cubic system (Mohs 10, the hardest known natural substance). Most gem diamonds form between 140 and 190 km depth in the earth's mantle and are brought to the surface by kimberlite volcanic eruptions. The major producing countries are Russia, Botswana, Canada, Angola, and South Africa. Diamond's brilliance results from its high refractive index (2.42) combined with strong light dispersion. Traditionally it represents endurance and eternal commitment, which is why it became the dominant engagement ring stone in the 20th century.
May: Emerald
Emerald is the green variety of beryl (Mohs 7.5–8), colored by chromium and sometimes vanadium in the beryl lattice. Nearly all natural emeralds contain inclusions and surface fractures (called the jardin), which are accepted in the trade to a degree not typical for other gems. Colombian mines (Muzo, Chivor, Coscuez) produce the most prized material; Zambia, Brazil, and Ethiopia also supply the market. Fracture filling with oils or resins is a standard and accepted trade treatment. Emerald is traditionally associated with renewal, love, and prosperity.
June: Pearl, Moonstone, and Alexandrite
June has three birthstones. Pearls form in the soft tissue of mollusks when an irritant is coated with nacre; natural pearls are rare, and virtually all commercial pearls are cultured. Pearl hardness is approximately 2.5–4.5 on the Mohs scale — among the softest gem materials — and pearls are damaged by acids, perfume, and hairspray. Moonstone is a feldspar mineral (Mohs 6–6.5) that displays adularescence, a billowing blue-white glow caused by the diffraction of light between alternating layers of orthoclase and albite. Alexandrite is a rare chrysoberyl variety (Mohs 8.5) that appears green in daylight and red-purple in incandescent light due to a chromium absorption band at the boundary of red and green wavelengths.
July: Ruby
Ruby is the red variety of corundum (Al2O3, Mohs 9). Its red color comes from chromium substituting for aluminum in the corundum lattice; the same substitution in blue material produces sapphire. Myanmar (Burma) produces the most prized pigeon-blood rubies; Mozambique, Thailand, Sri Lanka, and Madagascar are also major sources. Ruby is the second hardest natural mineral after diamond. In tradition, ruby is associated with passion, strength, and courage.
August: Peridot, Spinel, and Sardonyx
Peridot is the gem variety of olivine (Mg,Fe)2SiO4, Mohs 6.5–7. Its green color comes from iron in the olivine structure; the depth of green varies with iron content. Unusually, peridot has been found in meteorites (pallasite meteorites), making it one of the few gem minerals with an extraterrestrial occurrence. The primary source is the San Carlos Apache Reservation in Arizona; Pakistan, Myanmar, China, and Ethiopia also produce fine material. Spinel (MgAl2O4, Mohs 8) was added to the August list in 2016; historically many famous "rubies" in crown jewels were actually red spinels. In tradition, peridot is associated with purity and protection.
September: Sapphire
Sapphire is corundum (Al2O3, Mohs 9) in any color except red (which is ruby). Blue sapphire owes its color to iron-titanium charge transfer. Sapphire occurs in nearly every color: pink, yellow, orange, green, purple, and colorless. The most prized material comes from Kashmir (India), Myanmar, and Sri Lanka; Madagascar and Montana are significant modern sources. Sapphire is traditionally associated with loyalty, honesty, and wisdom.
October: Opal and Tourmaline
Opal is a hydrated amorphous silica (SiO2·nH2O, Mohs 5.5–6.5) containing up to 20% water. Its play-of-color — the spectrum of shifting colors visible in precious opal — results from diffraction of light by a regular grid of silica spheres of near-uniform size. Australia produces the majority of the world's fine opal. Because of its water content, opal is sensitive to rapid temperature changes and very low humidity, which can cause crazing. Tourmaline (complex boron silicate, Mohs 7–7.5) offers a wide color range, from colorless to black, including the green-to-pink watermelon variety. Opal is traditionally associated with hope and creativity.
November: Citrine and Topaz
Citrine is the yellow-to-brownish-orange variety of quartz (SiO2, Mohs 7). Most commercial citrine is produced by heat-treating amethyst at 470–560°C, which converts the violet iron color centers to yellow or orange. Natural unheated citrine is rarer and comes primarily from the Anahí mine in Bolivia. Topaz (Al2SiO4(F,OH)2, Mohs 8) occurs in many colors; blue topaz seen in the market is almost always produced by irradiating colorless topaz and then heating it. Both November stones are traditionally associated with warmth, calm, and abundance.
December: Turquoise, Tanzanite, and Zircon
Turquoise is a hydrated copper aluminum phosphate (CuAl6(PO4)4(OH)8·4H2O, Mohs 5–6) with a distinctive blue-to-green color from copper. It is typically porous and is commonly treated with waxes or resins to improve durability and surface appearance. Significant sources include Iran, the American Southwest, China, and Egypt. Tanzanite (a blue-violet variety of the mineral zoisite, Mohs 6–7) was discovered in 1967 near the Merelani Hills in Tanzania, the world's only known source; it is strongly trichroic, appearing blue, violet, or red depending on viewing direction. Zircon (ZrSiO4, Mohs 6–7.5) is one of the oldest known minerals on earth and occurs in a range of colors; blue zircon is produced by heat treatment. Turquoise is traditionally associated with peace and protection; tanzanite with balance and awareness.