October Birthstone — Opal and Tourmaline
October Birthstone — Opal and Tourmaline
Two distinct gems sharing the autumnal designation, with opal's play-of-colour and tourmaline's pinks and bicolours
The October birthstones in the modern American list are opal and tourmaline. Opal, the traditional choice, has been associated with October since at least the eighteenth century and was the original designation in the 1912 American National Retail Jewellers Association list. Tourmaline was added in 1952 by the Jewelry Industry Council to provide a more durable and widely available alternative, particularly in the form of pink tourmaline, which has become the most commonly marketed October birthstone after opal itself. Both AGTA and GIA recognise this dual designation today.
Opal as the traditional October stone
Opal is a hydrated silica gem (SiO2·nH2O) that displays the optical phenomenon called play-of-colour — flashes of spectral colours visible as the stone is moved or as the lighting changes. The play-of-colour arises from diffraction of light by an ordered three-dimensional array of silica spheres in the gem's structure; the colour of the diffracted light depends on the size and ordering of these spheres. Opal varieties include precious opal (white, black, and crystal opals showing play-of-colour), fire opal (orange to red without play-of-colour), and common opal (without significant play-of-colour).
Australia produces most of the world's high-end precious opal, including the famous black opal of Lightning Ridge, the white opal of Coober Pedy and Andamooka, and the boulder opal of Queensland. Ethiopia has emerged since 2008 as a major source of welo opal, including white opal with strong play-of-colour and treated black opal varieties. Mexico is the principal source of fire opal. The October birthstone tradition typically emphasises the play-of-colour varieties, but warm-toned fire opals also align well with the autumnal seasonal palette.
Opal is relatively soft (5.5 to 6.5 on the Mohs scale) and contains structural water, which makes it sensitive to thermal shock, dehydration, and chemical exposure. Care is correspondingly important; opal is best worn in pendants, earrings, and protected ring settings rather than exposed engagement-ring contexts.
Tourmaline as the durable alternative
Tourmaline was added as an October alternative in 1952 to provide a more durable and widely available option. Pink tourmaline is the most commonly marketed October birthstone tourmaline, but the species occurs in essentially every colour, with bi-coloured (watermelon) tourmaline, blue (indicolite), green, and rare colour-change varieties also relevant. Hardness of 7 to 7.5 makes tourmaline well-suited to ring wear, and the wide colour range allows buyers to choose stones across price tiers and aesthetic preferences.
Major tourmaline sources include Brazil (particularly Minas Gerais and Paraíba), Mozambique, Madagascar, Nigeria, Afghanistan, and the United States (notably California and Maine). Paraíba tourmaline — the rare neon-blue to neon-green copper-bearing variety — is at the top of the tourmaline market and commands prices that approach those of fine emerald and ruby. Routine pink, green, and bi-coloured tourmaline trades at much more accessible prices and supplies the bulk of October birthstone marketing.
The pairing in practice
The opal-and-tourmaline pairing offers October buyers genuine choice. Opal provides the optical drama of play-of-colour and the cultural depth of long birthstone association; tourmaline offers durability, colour variety, and accessibility. Retailers commonly stock both, with finer opals featuring in higher-tier collections and pink tourmalines providing volume and value across price points.
Both stones suit autumnal aesthetic expression — opal's play-of-colour can include warm spectral tones, and pink-to-red tourmaline provides direct seasonal reference. Custom and bespoke October birthstone work often combines the two, or pairs either with diamonds for added presence.