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May 21 – June 20 · Air

Gemini birthstones

Gemini carries Pearl and Agate in the zodiac tradition.

US births under Gemini
8.56% rank 4 of 12 signs
Born in June
65.1% of Gemini births
Fine for a daily ring
1 of 2 Agate

US SSA births 2000–2014 (FiveThirtyEight); our gemstone reference.

More on Gemini: the Gemini sign, Gemini horoscope today and Gemini compatibility.

The signs either side: Taurus birthstones and Cancer birthstones.

Gemini Birthstone: Pearl and Agate and What They Mean

Pearl

Composition Calcium carbonate (aragonite) in a matrix of conchiolin
Hardness · System 2.5–4.5 · Orthorhombic (aragonite)

Soft enough to scratch with a fingernail and dissolved by acid — perfume, vinegar and sweat all damage it.

Traditionally associated with sincerity, emotional maturity and quiet dignity.

Agate

Composition Banded chalcedony formed in volcanic cavities
Hardness · System 6.5–7 · Trigonal

The bands record successive deposits of silica in a gas bubble — each line is a separate episode of mineral-rich water passing through.

Traditionally associated with steadiness and gradual, unforced progress.

The reasoning

Why Gemini gets Pearl and Agate

Gemini is ruled by Mercury and symbolized by twins, and its stones are chosen for doubleness and quick change. Pearl grows in layers inside a shell and its luster shifts with the light; it belongs to June, the month in which Gemini ends. Agate is banded, line after line of different color in one stone, which suits a sign that holds several ideas at once. In crystal lore agate is the steadier, meant to slow a quick mind down long enough to finish what it started.

Other stones often given to Gemini

Alexandrite Citrine Tiger's Eye

Two systems, one birth date

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

Zodiac stones Pearl, Agate
Months it covers May and June
Stones of those months Emerald, Pearl, Moonstone, Alexandrite
In both systems Pearl

May 21 – June 20 — so the sign opens in one month and closes in another. Why the two lists never line up → · The monthly chart →

June supplies 20 of the sign’s days and May just 11, which tips the monthly chart toward Pearl, the June stone. May is also lighter in births than its days imply: 34.9% of the sign’s US births in 2000–2014, from 35.5% of its days.

Agate appears in neither the modern nor the traditional monthly list — one of just four such stones across the twelve signs.

May Emerald June Pearl, Moonstone, Alexandrite

The stones themselves

Stone Mohs Crystal system Main sources
Pearl 2.5–4.5 Orthorhombic (aragonite) Japan, China, Australia
Agate 6.5–7 Trigonal Brazil, India, Germany

Pearl (2.5–4.5) is better in a pendant than a ring, because of perfume, hairspray and sweat, which etch the nacre; Agate (6.5–7) is easy to wear every day — it is tough and needs nothing more than soapy water. What the scale means →

Gemini birthstones on the Mohs hardness scale
Gemini birthstones on the Mohs hardness scaleMohs scale with the Gemini zodiac stones (Pearl 2.5–4.5, Agate 6.5–7) filled and the stones of its calendar months outlined.Pearl: Mohs 2.5–4.5Pearl 2.5–4.5Agate: Mohs 6.5–7Agate 6.5–7Emerald: Mohs 7.5–8Emerald 7.5–8Moonstone: Mohs 6–6.5Moonstone 6–6.5Alexandrite: Mohs 8.5Alexandrite 8.5Garnet: Mohs 6.5–7.5Amethyst: Mohs 7Citrine: Mohs 7Rose Quartz: Mohs 7Clear Quartz: Mohs 7Smoky Quartz: Mohs 7Aquamarine: Mohs 7.5–8Emerald: Mohs 7.5–8Bloodstone: Mohs 6.5–7Peridot: Mohs 6.5–7Sardonyx: Mohs 6.5–7Zircon: Mohs 6–7.5Carnelian: Mohs 6.5–7Onyx: Mohs 6.5–7Agate: Mohs 6.5–7Tiger's Eye: Mohs 6.5–7Aventurine: Mohs 6.5–7Diamond: Mohs 10Pearl: Mohs 2.5–4.5Alexandrite: Mohs 8.5Moonstone: Mohs 6–6.5Labradorite: Mohs 6–6.5Pyrite: Mohs 6–6.5Ruby: Mohs 9Sapphire: Mohs 9Spinel: Mohs 8Topaz: Mohs 8Opal: Mohs 5.5–6.5Rhodonite: Mohs 5.5–6.5Tourmaline: Mohs 7–7.5Turquoise: Mohs 5–6Lapis Lazuli: Mohs 5–6Hematite: Mohs 5–6Tanzanite: Mohs 6–7Jade: Mohs 6–7Obsidian: Mohs 5–5.5Malachite: Mohs 3.5–4Amber: Mohs 2–2.5Selenite: Mohs 2Fluorite: Mohs 4Sodalite: Mohs 5.5–6Kyanite: Mohs 4.5–7Lepidolite: Mohs 2.5–31Talc2Gypsum3Calcite4Fluorite5Apatite6Orthoclase7Quartz8Topaz9Corundum10Diamondfingernail 2.5window glass 5.5household dust (quartz) 7Source: Mohs scale minerals · ranges from our 43-stone referenceastrohot.com
Gemini birthstones on the Mohs hardness scaleMohs scale with the Gemini zodiac stones (Pearl 2.5–4.5, Agate 6.5–7) filled and the stones of its calendar months outlined.Pearl: Mohs 2.5–4.5Pearl 2.5–4.5Agate: Mohs 6.5–7Agate 6.5–7Emerald: Mohs 7.5–8Emerald 7.5–8Moonstone: Mohs 6–6.5Moonstone 6–6.5Alexandrite: Mohs 8.5Alexandrite 8.51Talc2Gypsum3Calcite4Fluorite5Apatite6Orthoclase7Quartz8Topaz9Corundum10Diamondfingernail 2.5glass 5.5dust 7Source: Mohs scale minerals · ranges from our 43-stone referenceastrohot.com

Gemini’s zodiac stones: Pearl 2.5–4.5, Agate 6.5–7. The May and June month stones it also covers: Emerald 7.5–8, Moonstone 6–6.5, Alexandrite 8.5. Emerald and Alexandrite stay at 7 or harder across their whole range, so dust cannot scratch them.

Cite this page

AstroHot. “Gemini Birthstone: Pearl and Agate and What They Mean.” Accessed October 27, 2026. https://astrohot.com/birthstones/by-zodiac/gemini/

For Wikipedia {{cite web |title=Gemini Birthstone: Pearl and Agate and What They Mean |url=https://astrohot.com/birthstones/by-zodiac/gemini/ |website=AstroHot |access-date=2026-10-27}}