October Birthstones

October has two official birthstones: opal, on the list since 1912, and tourmaline, added in 1952. Between them they cover almost every color a gemstone can show, from the shifting flashes of opal to the greens, blues, pinks and reds of tourmaline.

Opal is hydrated silica with no crystal structure. In precious opal, tiny silica spheres packed in orderly rows split light into flashes of spectral color, an effect known as play-of-color. Most opal today comes from Australia and Ethiopia. Ethiopian opal is often hydrophane, meaning it can absorb water and temporarily change in appearance, so it is best kept away from liquids and oils. Opal is a softer stone, best in pendants and earrings, or rings worn with care.

Tourmaline is a group of complex borosilicate minerals with one of the widest color ranges of any gem species, including crystals that show two or more colors. Deep pink to red tourmaline is traded as rubellite, and it is included in this collection. Tourmaline is durable enough for everyday jewelry.

Every stone here is natural, photographed individually and listed with its exact weight, dimensions and treatment status.

Month: October
Official birthstones: Opal, Tourmaline
In this collection: Opal, Tourmaline (including rubellite)
Hardness (Mohs): Opal 5.5 to 6.5, Tourmaline 7 to 7.5