May 21 – June 20 · Air

Gemini birthstones

Gemini carries Pearl and Agate in the zodiac tradition.

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.

Sign or month?

Gemini runs May 21 – June 20, 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 →

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