What is the Cancer birthstone?

There isn't one settled answer. The traditional tropical zodiac (June 21 – July 22) names Emerald; the modern jewelry-trade convention names Ruby instead. Both are sourced, dated lists — see the comparison table above.

Why do the two zodiac birthstone lists disagree for Cancer?

Cancer begins in June, but its traditional stone, Emerald, does not appear in the historical June birthstone list — this is the one sign where that pattern, which explains the other eleven, breaks down. Its modern stone, Ruby, comes from the separate current monthly birthstone table.

What color is Ruby, Cancer's modern birthstone?

Ruby occurs in red tones, with a Mohs hardness of 9.

Is my Vedic sign the same as Cancer?

Not necessarily. The sidereal zodiac used in Vedic astrology runs roughly 23 days behind the tropical zodiac, so a birth date in tropical Cancer often falls under sidereal Gemini instead. We have not sourced Vedic birthstone assignments, so this concerns the sign only, not a stone recommendation.

Why doesn't Cancer follow the same month-to-sign pattern as the other eleven signs?

Cancer begins in June, and the historical June entry named cat's eye, turquoise, and agate — none of which is emerald, the stone the traditional tropical zodiac actually assigns to Cancer. Every other sign's tropical stone traces directly, or through a variety relationship, back to its starting month's historical entry. Cancer is the one exception we could not source an explanation for, so we're reporting the gap rather than guessing at a reason.

Cancer Birthstones

Cancer doesn't have one settled birthstone. The traditional tropical zodiac assigns Emerald; the modern jewelry trade assignsRuby instead. Both are attested, dated conventions — not ancient absolutes — and the comparison and sourcing below show exactly where each one comes from.

Cancer at a glance

Date range: June 21 – July 22
Element: Water
Modality: Cardinal
Ruling planet: Moon
Polarity: Negative

Cancer birthstones by system

Both zodiac-birthstone systems for Cancer, side by side
Sign	Traditional tropical zodiacTraditional Western astrology	Modern jewellery-trade zodiacContemporary retail convention
Cancer	Emerald	Ruby

Traditional tropical zodiac: This list derives from the historical monthly birthstone table keyed to each sign's starting month, so it inherits that table's lack of a single standardising source.

Modern jewellery-trade zodiac: This is a contemporary retail convention mapping the current monthly list onto zodiac date ranges — a 20th/21st-century commercial construct, not an ancient astrological tradition.

The stones themselves

Emerald (traditional tropical zodiac)

Emerald is a variety of Beryl. Mohs hardness: 7.5–8. Color: Green. Emerald is the green, chromium- and/or vanadium-bearing variety of beryl; inclusions ("jardin") are so characteristic that flawless emeralds are treated with suspicion by gemologists.

Ruby (modern jewelry-trade zodiac)

Ruby is a variety of Corundum. Mohs hardness: 9. Color: Red. Ruby is the red variety of corundum, colored by chromium; every other gem-quality color of corundum is classed as sapphire.

Why Cancer has two different stones

Cancer is the one sign where this derivation breaks down. It begins in June, and the historical June list named Cat's Eye, Turquoise, and Agate — none of which is Emerald, the stone the traditional tropical zodiac actually assigns to Cancer. We do not have a sourced explanation for why Cancer departs from the pattern that holds for the other eleven signs, so we are reporting the gap rather than guessing at a reason.

The modern jewelry-trade list works differently: rather than drawing on the historical table, it draws on the current monthly birthstone table instead. Cancer ends in July, and its modern stone, Ruby, matches the current US birthstone table for July — the month that holds most of Cancer's date range.

Western vs. Vedic: which sign are you really?

The dates above use the tropical zodiac, the system Western astrology — and this page — is built on. The sidereal zodiac used in Vedic (Jyotish) astrology runs roughly 23 days behind it, because it tracks the actual position of the constellations rather than the seasons. If you were born under tropical Cancer (June 21 – July 22), your sidereal placement is often Gemini instead — especially for birthdays in the first few weeks of the range. We have not sourced Vedic birthstone assignments for Gemini or any other sign, so this is a note about the sign shift only, not a birthstone recommendation.

Cancer birthstone FAQ

What is the Cancer birthstone?: There isn't one settled answer. The traditional tropical zodiac (June 21 – July 22) names Emerald; the modern jewelry-trade convention names Ruby instead. Both are sourced, dated lists — see the comparison table above.
Why do the two zodiac birthstone lists disagree for Cancer?: Cancer begins in June, but its traditional stone, Emerald, does not appear in the historical June birthstone list — this is the one sign where that pattern, which explains the other eleven, breaks down. Its modern stone, Ruby, comes from the separate current monthly birthstone table.
What color is Ruby, Cancer's modern birthstone?: Ruby occurs in red tones, with a Mohs hardness of 9.
Is my Vedic sign the same as Cancer?: Not necessarily. The sidereal zodiac used in Vedic astrology runs roughly 23 days behind the tropical zodiac, so a birth date in tropical Cancer often falls under sidereal Gemini instead. We have not sourced Vedic birthstone assignments, so this concerns the sign only, not a stone recommendation.
Why doesn't Cancer follow the same month-to-sign pattern as the other eleven signs?: Cancer begins in June, and the historical June entry named cat's eye, turquoise, and agate — none of which is emerald, the stone the traditional tropical zodiac actually assigns to Cancer. Every other sign's tropical stone traces directly, or through a variety relationship, back to its starting month's historical entry. Cancer is the one exception we could not source an explanation for, so we're reporting the gap rather than guessing at a reason.

Sources

Retrieved 2026-08-10.