October has two birthstones: opal and tourmaline. Opal is prized for play-of-color, shifting rainbow flashes, and measures 5 to 6.5 on the Mohs scale; tourmaline comes in more colors than almost any gem and measures 7 to 7.5.
Opal can crack from the heat of strong light alone. The Gemological Institute of America (GIA) warns that “heat from intense light can cause fracture lines called ‘crazing,'” and that “the only safe way to clean opal is with warm, soapy water.”
Tourmaline’s name comes from the Sinhalese toramalli, “stone with mixed colors,” and a single crystal can be pink at one end and green at the other. The British birthstone list includes only opal for October, while the U.S. list adds tourmaline.
Table of Contents
What are the October birthstones?
Opal and tourmaline are both official October birthstones on the GIA list; the British list includes opal only. The table compares them.
| Property | Opal | Tourmaline |
|---|---|---|
| Material | Opal (hydrated silica) | Tourmaline mineral group |
| Mohs hardness | 5–6.5 | 7–7.5 |
| Toughness | Poor to fair | Fair |
| Key feature | Play-of-color | Widest color range of any gem family |
| Main sources | Australia (dominant); also Ethiopia, Mexico, Brazil, Central Europe, Honduras, Indonesia, Madagascar, Peru, Turkey, United States | Brazil (primary); also Afghanistan, Pakistan, Kenya, Madagascar, Mozambique, United States (California, Maine) |
| Wedding anniversary | 14th | 8th |
| On UK list | Yes | No |
| Zodiac signs for October birthdays | Libra (to about October 22) and Scorpio (from about October 23) | Same |
Why does October have two birthstones?
Opal is the traditional October stone; tourmaline was added to the U.S. list in 1952 as a harder, more varied alternative. The full month-by-month comparison is in the Birthstones by Month chart.
October birthstone colors
The October birthstone color depends on the stone: opal shows flashes of rainbow color over a white, black, orange or clear background, and tourmaline ranges from pink and red to green, blue and black. The two stones cover more colors between them than any other birthstone month.
Types of opal for an October birthstone
Opal is classified by its background color and origin, and each main type is linked to a specific place. GIA identifies these types:
| Opal type | Appearance | Main source |
|---|---|---|
| Black opal | Play-of-color against a dark body | Lightning Ridge, Australia |
| White opal | Play-of-color against a light body | White Cliffs, Mintabie, Andamooka, Coober Pedy (Australia) |
| Boulder opal | Opal in veins within ironstone host rock | Queensland, Australia (only source) |
| Fire opal | Yellow, orange or red body color | Mexico |
| Crystal opal | Transparent to translucent with play-of-color | Several sources |
Types of tourmaline for an October birthstone
Tourmaline varieties are named by color, and some of the most valuable owe their color to copper or chromium.
| Tourmaline variety | Color |
|---|---|
| Pink tourmaline | Pink; often marketed specifically as the October stone |
| Rubellite | Red |
| Chrome tourmaline | Emerald green |
| ParaÃba-type tourmaline | Neon green to blue-violet, colored by copper; discovered in ParaÃba State, Brazil, in the late 1980s, later in Mozambique and Nigeria |
| Watermelon tourmaline | Pink core with a green rim |
| Black tourmaline (schorl) | Black |
October birthstone meaning and history
Opal’s name is believed to come from the Sanskrit upala, meaning “precious stone,” which became opalus in ancient Rome. GIA records the following lore and history:
| Stone | History and lore |
|---|---|
| Opal | Ancient Greeks believed opals granted “the gift of prophesy and protection from disease” |
| Opal | Europeans regarded opal as “a symbol of purity, hope and truth” |
| Tourmaline | In the 1500s, a Spanish conquistador found green tourmaline crystals in Brazil and mistook them for emerald |
| Tourmaline | Pink tourmaline is associated with love and compassion; green with courage and strength; black with protection |
These beliefs are folklore; they describe tradition, not gemological properties. Green tourmaline’s history of being mistaken for emerald parallels peridot’s; the May Birthstone guide explains what makes a true emerald.
Choosing and caring for an October birthstone
Tourmaline is the better October birthstone for an everyday ring, at 7 to 7.5 on the Mohs scale; opal, at 5 to 6.5 with poor to fair toughness, suits pendants and earrings or protective settings. GIA gives these care rules:
- Opal: clean only with warm, soapy water; never use ultrasonic or steam cleaners; keep it away from heat and intense light, which can cause crazing; avoid hydrofluoric acid and caustic alkaline solutions (GIA opal care).
- Opal treatments: opals may be impregnated with oil, wax or plastic, or given sugar or smoke treatments; ask before buying.
- Tourmaline: clean with warm, soapy water and a soft brush; avoid ultrasonic and steam cleaners, which can damage stones with liquid inclusions (GIA tourmaline care).
- Tourmaline treatments: heat-treatment color is stable, but “color changes due to irradiation can fade with exposure to heat or bright light.”
Assembled opals, doublets and triplets made of a thin opal layer glued to a backing, should not be soaked, because water can loosen the adhesive.
What the October birthstone is not
The October birthstones are often misunderstood. The points below separate the facts.
- Opal is not a crystal mineral. It is hydrated silica without a regular crystal structure.
- Tourmaline is not one color. It occurs in pink, red, green, blue, black and multicolored varieties.
- Opal is not a good choice for rough daily wear. It scratches and cracks more easily than most birthstones.
- October does not have only one birthstone in the U.S. Tourmaline joined opal in 1952; the UK list keeps opal alone.
Frequently asked questions
What color is the October birthstone?
The October birthstone color can be opal’s multicolored play-of-color or tourmaline’s pink, red, green or blue. Pink tourmaline is the tourmaline most often sold as the October stone.
Which October birthstone is more durable?
Tourmaline is more durable, at 7 to 7.5 on the Mohs scale, than opal, which measures 5 to 6.5 with poor to fair toughness.
What anniversary is opal for?
Opal is the gemstone for the 14th wedding anniversary, and tourmaline for the 8th, according to GIA.
