Short answer: October has two birthstones: opal and tourmaline. Opal is known for play-of-color, flashes of rainbow light that shift as the stone moves. Tourmaline comes in more colors than almost any other gem, with pink tourmaline the traditional October choice. Opal is softer and more delicate; tourmaline is harder and suits everyday wear.
Why does October have two birthstones?
Opal is the traditional October birthstone and was the one on the 1912 list adopted in the United States. When the list was updated in 1952, pink tourmaline was added as a second October stone. Today tourmaline of any color is accepted.
Opal
What is opal?
Opal is a hydrated, amorphous form of silica: silicon dioxide with water held inside it, usually around 6 to 10 percent by weight. Because it has no crystal structure, it is classed as a mineraloid rather than a mineral. It rates 5 to 6.5 on the Mohs scale, softer than most gemstones.
Why does opal flash with color?
Precious opal is made of microscopic spheres of silica stacked in an orderly grid. When light passes through the gaps between the spheres, it is split into spectral colors, an effect called diffraction. The size of the spheres decides which colors appear. As you move the stone, the colors shift and flash. This is called play-of-color.
Common opal lacks that orderly structure and shows no play-of-color, though it can still be attractive. Colored opal without flashes, such as many of the green and pink opals sold as tumbled stones and carvings, is common opal.
What kinds of opal are there?
- White opal has a light body color with play-of-color.
- Black opal has a dark body that makes the colors stand out. Lightning Ridge in New South Wales, Australia, is famous for it.
- Boulder opal comes from only one place in the world: Queensland, Australia.
- Fire opal is transparent to translucent yellow, orange or red, from Querétaro in Mexico, sometimes with play-of-color.
- Ethiopian opal from Wollo Province comes in white, yellow, orange, brownish red and chocolate brown body colors.
Where is opal found?
The fields of Australia are the most productive in the world, and Australian opal has been cited as accounting for 95 to 97 percent of the world's precious opal. Ethiopia, Mexico and Brazil are also important sources, with smaller deposits in Central Europe, Honduras, Indonesia, Madagascar, Peru, Turkey and the United States.
What is opal traditionally associated with?
The name is believed to come from the Sanskrit upala, "precious stone", which became opalus in ancient Rome. Bedouins once believed opal held lightning and fell from the sky during storms. Europeans long held it to be a symbol of purity, hope and truth, and in the Middle Ages it was thought to carry the virtues of every gem whose color it showed.
Its reputation darkened after 1829, when Sir Walter Scott's novel Anne of Geierstein featured a cursed opal talisman. The idea that opal is unlucky followed from fiction, not tradition. Opal is the gem of the fourteenth wedding anniversary.
Tourmaline
What is tourmaline?
Tourmaline is a group of complex boron silicate minerals. It rates 7 to 7.5 on the Mohs scale, durable enough for everyday wear. It forms long, striated crystals, and it often shows two or more colors in one crystal.
The name comes from the Sinhalese word toramalli, often translated as "stone with mixed colors".
What colors does tourmaline come in?
Very few gems match tourmaline's range of color.
- Pink and red tourmaline, called rubellite, is the traditional October color.
- Green tourmaline, including the deep green "chrome" variety.
- Watermelon tourmaline is pink at the center and green on the outside, like a slice of the fruit.
- Black tourmaline, called schorl, is by far the most common kind, possibly 95 percent or more of all tourmaline in nature. It is collected as a mineral rather than cut as a gem.
- Paraíba tourmaline is an electric green to blue to violet, colored by traces of copper. It entered the market in the late 1980s from Paraíba State in Brazil, and similar copper-bearing tourmaline was later found in Mozambique and Nigeria.
A gem often mistaken for others
Because of its range of colors, tourmaline was confused with other gems for centuries. A Spanish conquistador who found green tourmaline in Brazil in the 1500s took it for emerald. One of the "rubies" in the Russian crown jewels, the Caesar's Ruby pendant, is red tourmaline. Scientists recognized tourmaline as a distinct mineral species only in the 1800s.
Tourmaline is also pyroelectric: warmed, it becomes electrically charged and can attract and then repel light ash. That earned it the old nickname "Ceylonese magnet".
Where is tourmaline found?
Brazil is the most common source, and most Brazilian tourmaline has come from pegmatites in the state of Minas Gerais. The pegmatite guide explains how those rocks grow large crystals. Tourmaline is also mined in Afghanistan, Pakistan, Kenya, Madagascar and Mozambique. In the United States, California and Maine are historically important producers; the first tourmaline find in Maine was made by two students on Mount Mica in 1821.
What is tourmaline traditionally associated with?
In tradition, each color carries its own meaning. Black tourmaline is believed to protect the wearer and give a sense of confidence. Pink tourmaline is associated with love, compassion and gentleness. Green tourmaline is associated with courage and strength. Ancient mystics were said to believe tourmaline could inspire artistic expression. It is the gem of the eighth wedding anniversary.
These are traditions and beliefs, not properties of the stones.
Opal or tourmaline: which should you choose?
| Opal | Tourmaline | |
|---|---|---|
| Material | Hydrated amorphous silica | Boron silicate mineral group |
| Hardness (Mohs) | 5 to 6.5 | 7 to 7.5 |
| Look | Play-of-color flashes | Saturated colors, often two in one stone |
| Best for | Pendants, earrings, protected rings | Rings and everyday jewelry |
How do you care for October birthstones?
- Opal: clean with warm, soapy water only. Avoid high heat and sudden temperature changes, which can fracture it. Do not soak opal doublets or triplets, which are thin slices of opal glued to a backing; long contact with water can weaken the glue. Store opal separately, since harder gems such as diamond, ruby, sapphire and emerald can scratch it.
- Tourmaline: clean with warm, soapy water and a soft brush. Do not use ultrasonic or steam cleaners, and keep it away from heat.
How can you tell natural opal?
- Doublets and triplets show a flat, layered side view, with a dark backing and, in a triplet, a clear quartz dome on top. They are real opal, but they should be described as assembled.
- Treated opal may be impregnated with oil, wax or plastic.
- Synthetic opal is too regular: under magnification its patches of color line up in a repeating "lizard skin" or "chicken wire" pattern, and it does not fluoresce under ultraviolet light the way much natural opal does.
Browse crystals and minerals at Digital Towns Market
Digital Towns Market
Opal and tourmaline in stock
Frequently asked questions
What is the October birthstone color?
October has no single color. Opal shows flashes of every spectral color, and tourmaline comes in pink, red, green, blue, black and more. Pink is the traditional October tourmaline color.
Is opal bad luck?
No. The idea comes from fiction: Sir Walter Scott's 1829 novel Anne of Geierstein featured a cursed opal talisman. Older traditions treated opal as lucky and as a symbol of hope and purity.
Can opal get wet?
Solid opal can be cleaned with warm, soapy water. Opal doublets and triplets should not be soaked, because long contact with water can weaken the glue that holds the layers together.
What is the rarest kind of tourmaline?
Copper-bearing Paraíba tourmaline from Brazil, Mozambique and Nigeria commands the highest prices, especially in intense neon blue to green.
What is watermelon tourmaline?
A tourmaline crystal that is pink at its core and green on the outside, from changes in chemistry while the crystal grew. Cut across, a slice looks like watermelon.
Sources
- GIA, October Birthstones: https://www.gia.edu/birthstones/october-birthstones
- GIA, Opal: https://www.gia.edu/opal
- GIA, Tourmaline: https://www.gia.edu/tourmaline
- American Gem Society, October Birthstone: https://www.americangemsociety.org/birthstones/october-birthstone/
- Wikipedia, Opal: https://en.wikipedia.org/wiki/Opal
- Wikipedia, Tourmaline: https://en.wikipedia.org/wiki/Tourmaline