October has two stones on the modern list, opal and tourmaline, and one on the traditional list, opal.
The two lists for October
Modern list (American Gem Society): Opal, Tourmaline
Traditional list (United Kingdom, National Association of Goldsmiths, 1937): Opal
There is no single official birthstone list, so you are free to choose whichever you prefer. You can check any month with our birthstone finder.
About the stones
Opal
Opal is hydrated silica, hardness about 5.5 to 6.5, that shows a play of colour from tiny spheres of silica that diffract light. Australia produces most of the world’s opal, including the fields of Coober Pedy and Lightning Ridge, and Ethiopia is a major modern source. Opal contains water, so it is sensitive to heat and dryness and can crack if it dries out. The belief that opal is unlucky is often traced to a nineteenth-century novel, and it is a superstition that is not well supported by the older history of the stone.
Tourmaline
Tourmaline is a mineral family found in almost every colour, sometimes several in one crystal, as in the pink and green watermelon tourmaline. Its hardness is 7 to 7.5. Brazil, Africa and Afghanistan are important sources. See the black tourmaline guide.
How the idea developed
October shows a change on the American list, where tourmaline joined opal to give a wider range of colours and prices. The traditional United Kingdom list of 1937 holds only opal. Because tourmaline comes in so many colours, it is a good choice for anyone who wants a modern October stone that is not opal.
For the wider history of the idea, see our birthstones overview. The modern list follows the American Gem Society, and the traditional list follows the 1937 United Kingdom list, both summarised in Wikipedia, Birthstone.
A different system
Vedic gemstone (ratna) guidance is a different system from birthstones. It is tied to the nine planets and to a birth chart, not to the calendar month, and it belongs to the Vedic tradition, which is covered on our sister site, Nidarshana Vedh. Nothing on this page is Vedic advice.
A note on health. Crystals are valued for beauty, meaning and ritual. There is no scientific evidence that they treat health conditions. If you are struggling with your health or mood, please speak to a doctor.
Frequently asked questions
↳ Is opal unlucky?
That is a superstition, often traced to a nineteenth-century novel, and it is not found in the oldest traditions. Opal has been valued for centuries.
↳ How should I care for opal?
Keep it out of heat and very dry air, avoid soaking, and wipe it gently with a soft cloth.