What Is My Birthstone?
October Birthstone: Opal, Tourmaline
Opal, Tourmaline
October has two birthstones: opal, the traditional stone, and tourmaline, added in 1912 as a durable alternative. Opal is hardened silica gel whose microscopic spheres diffract light into the rainbow flashes called play-of-color. Tourmaline is a crystalline boron silicate that comes in more colors than any other gem, with pink the classic October choice.
Australia supplies most of the world's precious opal, including black opal from Lightning Ridge, while Ethiopia has become a major source of bright crystal opal since 2008. Because opal contains water, it is soft (Mohs 5.5–6.5) and should be kept away from heat and hard knocks.
Pink and watermelon tourmaline give October a hard-wearing gem for rings, and the neon Paraíba tourmaline from Brazil is among the most valuable colored stones on Earth.
October birthstones at a glance
- Modern birthstones: Opal, Tourmaline
- Traditional birthstone: Opal
- Color: white or black with rainbow play-of-color (opal), pink to watermelon (tourmaline)
- Traditionally associated with creativity, hope and inspiration
About Opal
Opal is famous for its play-of-color, caused by the diffraction of light through microscopic silica spheres. Australia produces 95% of the world's opals.
| Type | Semi-Precious Stones |
|---|---|
| Chemical formula | SiO2·nH2O |
| Mohs hardness | 5.5 |
| Crystal system | amorphous |
| Luster | vitreous |
| Streak | White |
| Cleavage | None |
- Australia produces about 95% of the world's precious opal
- Opals contain up to 20% water
- The Romans called opal 'cupid paederos' (child beautiful as love)
How to tell real Opal at a glance
- Color: White, Black, Fire, Blue, Pink. Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue.
- Luster: Vitreous. Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner.
- Transparency: Translucent. Hold a thin edge up to a bright light and note whether light passes through.
- Mohs hardness: 5.5. It is about as hard as window glass: a knife barely marks it, while a steel file (Mohs 6.5) will.
Other stones on this page
Frequently asked questions
What is the birthstone for October?
The modern October birthstone is Opal, Tourmaline.
What color is the October birthstone?
Opal is white or black with rainbow play-of-color (opal), pink to watermelon (tourmaline).
Is opal bad luck?
The superstition comes from a 19th-century novel and a dip in opal sales that followed. Opal was considered a lucky stone for most of history and is simply a delicate gem that needs gentle care.
How can I tell real opal from synthetic or opalite?
Natural opal has irregular, patchy color flashes; synthetic opal shows a regular snakeskin or columnar pattern; opalite is glass with a milky blue glow and no true play-of-color.
