June 21 – July 22 · Water

Cancer birthstones

Cancer carries Ruby and Moonstone in the zodiac tradition.

Ruby

Composition Aluminium oxide (Al₂O₃) — corundum coloured by chromium
Hardness · System 9 · Trigonal

Ruby and sapphire are the same mineral. Red corundum is ruby; every other colour is sapphire.

Traditionally associated with courage, appetite for life and decisive action.

Moonstone

Composition Potassium aluminium silicate (KAlSi₃O₈) — feldspar
Hardness · System 6–6.5 · Monoclinic

The floating blue glow is adularescence — light scattering between microscopic layers of two feldspars, not an inclusion or a coating.

Traditionally linked to intuition, cycles and new beginnings.

Sign or month?

Cancer runs June 21 – July 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 →

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