October birthstones: opal and tourmaline
October has two officially accepted birthstones — opal (traditional) and tourmaline (modern, added in 1952). Each is a different proposition.
The two options
| Hardness | What it does | Best for | |
|---|---|---|---|
| Opal | 5.5–6.5 | Play-of-color — flashing rainbow as it tilts | Earrings, pendants, special-occasion rings. Too soft for daily-wear rings. See the opal guide. |
| Tourmaline | 7–7.5 | Every color, often two in one stone (watermelon) | Daily-wear rings, the harder choice. Paraíba (neon blue), rubellite (red), and watermelon (bi-color) are the standouts. See the tourmaline guide. |
For a daily-wear ring, default to tourmaline. For a dramatic special-occasion piece or a pendant/earring set, opal is the more distinctive choice — nothing else does what play-of-color does.
See the deeper guides: opal and tourmaline.
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Browse tourmalines
More from the birthstones guides
Written by
Anna
Jeweler · Formi Jewelry
Anna works with Formi clients on stone selection, setting design, and fit — making sure every piece is right before it’s made.
Book a consultation with our in-house jewelersLast updated May 2026