October is the month with two birthstones at opposite poles. Opal is hydrated silica, and the ordered spheres inside it diffract light into a play-of-color no two stones repeat; the black opals of Lightning Ridge set the top of the scale. Tourmaline is the widest-ranging gem family there is, from rubellite pink through chrome green to parti-color stones cut to show two colors at once. Our October birthstone guide begins with opal and follows the month from there.
Here the two share a room: vintage and estate opal rings and pendants in their Victorian and mid-century settings, tourmalines in every direction the family runs, and modern pieces built around single remarkable stones.
They part ways on care. Tourmaline, at 7 to 7.5 on the Mohs scale, wears easily with routine sense. Opal is softer, 5.5 to 6.5, and holds water in its structure, so it prefers pendants and earrings for constant wear, dislikes prolonged heat and dryness, and should never see an ultrasonic cleaner. Our care guide treats each on its own terms.
The full year of stones lives in our birthstone jewelry guide.
