September 23 – October 22 · Air

Libra birthstones

Libra carries Opal and Peridot in the zodiac tradition.

Opal

Composition Hydrated silica (SiO₂·nH₂O) — 3 to 21 percent water by weight
Hardness · System 5.5–6.5 · Amorphous

The play of colour comes from stacked silica spheres diffracting light — the same physics as a butterfly wing, not pigment.

Traditionally linked to imagination, emotional range and creative flow.

Peridot

Composition Magnesium iron silicate ((Mg,Fe)₂SiO₄) — gem-quality olivine
Hardness · System 6.5–7 · Orthorhombic

Peridot arrives on Earth in meteorites — pallasite meteorites carry gem-quality crystals formed beyond this planet.

Traditionally linked to lightness, release of resentment and fresh perspective.

Sign or month?

Libra runs September 23 – October 22, which crosses two calendar months — so the zodiac stone and the monthly birthstone may or may not agree depending on your exact date. Neither system overrules the other; the zodiac one is simply older.

Compare against the monthly chart →

← All zodiac birthstones

Two systems, one birth date

Libra spans 2 calendar months, so you have more than one birthstone

Zodiac stones Opal, Peridot
Months it covers September and October
Stones of those months Sapphire, Opal, Tourmaline
In both systems Opal

September 23 – October 22 — so the sign opens in one month and closes in another. Why the two lists never line up →

The split is uneven: 8 days fall in September and 22 in October. So most people with this sign — 73% — are sold the October stone.

Both stones — Opal and Peridot — also sit in the monthly list somewhere, which is the usual case.

September Sapphire October Opal, Tourmaline

The stones themselves

Stone Mohs Crystal system Main sources
Opal 5.5–6.5 Amorphous Australia, Ethiopia, Mexico
Peridot 6.5–7 Orthorhombic Pakistan, Myanmar, USA (Arizona)

Opal is the softer at 5.5–6.5 on the Mohs scale — below 7, which means household dust scratches it, so it belongs in earrings or a pendant rather than an everyday ring. What the scale means →

Opal

Hydrated silica (SiO₂·nH₂O) — 3 to 21 percent water by weight Roman writers ranked it among the most valuable of gems; Australia has dominated supply since the 1890s

Peridot

Magnesium iron silicate ((Mg,Fe)₂SiO₄) — gem-quality olivine Mined on the Egyptian island of Zabargad for over 3500 years