2027 Forecast

June 21 – July 22 · Water

Cancer birthstones

Cancer carries Ruby and Moonstone in the zodiac tradition.

US births under Cancer
8.84% rank 3 of 12 signs
Born in July
69.0% of Cancer births
Fine for a daily ring
1 of 2 Ruby

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

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

The signs either side: Gemini birthstones and Leo birthstones.

Cancer Birthstone: Ruby and Moonstone and What They Mean

Ruby

Composition Aluminum oxide (Al₂O₃) — corundum colored by chromium
Hardness · System 9 · Trigonal

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

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

Moonstone

Composition Potassium aluminum 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.

The reasoning

Why Cancer gets Ruby and Moonstone

Cancer is the only sign ruled by the Moon, and moonstone, with its pale sheen that seems to move as the stone turns, is the obvious match: tradition ties it to the Moon's cycles, to home and to feeling. Ruby, the July stone, is the less expected choice. It supplies what the sign keeps hidden under its shell — warmth, fierce protectiveness and a heart far braver than it lets on. Soft outside and red-hot inside is a fair description of Cancer.

Other stones often given to Cancer

Pearl Selenite Aquamarine

Two systems, one birth date

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

Zodiac stones Ruby, Moonstone
Months it covers June and July
Stones of those months Pearl, Moonstone, Alexandrite, Ruby
In both systems Ruby, Moonstone

June 21 – July 22 — so the sign opens in one month and closes in another. Why the two lists never line up → · The monthly chart →

July supplies 22 of the sign’s days and June just 10, which tips the monthly chart toward Ruby, the July stone. Births follow the calendar closely here: in 2000–2014, June took 31.0% of the sign’s US births for 31.3% of its days.

In the monthly chart, Ruby is July’s modern birthstone; Moonstone is June’s modern birthstone. Both months fall inside Cancer, so here the two systems agree.

June Pearl, Moonstone, Alexandrite July Ruby

The stones themselves

Stone Mohs Crystal system Main sources
Ruby 9 Trigonal Myanmar, Mozambique, Thailand
Moonstone 6–6.5 Monoclinic Sri Lanka, India, Madagascar

Ruby (9) suits an everyday ring if you watch for glass filling — ask whether the stone is treated; Moonstone (6–6.5) can be worn often with care around hard knocks, which can split it along a cleavage plane. What the scale means →

Cancer birthstones on the Mohs hardness scale
Cancer birthstones on the Mohs hardness scaleMohs scale with the Cancer zodiac stones (Ruby 9, Moonstone 6–6.5) filled and the stones of its calendar months outlined.Ruby: Mohs 9Ruby 9Moonstone: Mohs 6–6.5Moonstone 6–6.5Pearl: Mohs 2.5–4.5Pearl 2.5–4.5Alexandrite: 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
Cancer birthstones on the Mohs hardness scaleMohs scale with the Cancer zodiac stones (Ruby 9, Moonstone 6–6.5) filled and the stones of its calendar months outlined.Ruby: Mohs 9Ruby 9Moonstone: Mohs 6–6.5Moonstone 6–6.5Pearl: Mohs 2.5–4.5Pearl 2.5–4.5Alexandrite: Mohs 8.5Alexandrite 8.51Talc2Gypsum3Calcite4Fluorite5Apatite6Orthoclase7Quartz8Topaz9Corundum10Diamondfingernail 2.5glass 5.5dust 7Source: Mohs scale minerals · ranges from our 43-stone referenceastrohot.com

Cancer’s zodiac stones: Ruby 9, Moonstone 6–6.5. The June and July month stones it also covers: Pearl 2.5–4.5, Alexandrite 8.5. Ruby and Alexandrite stay at 7 or harder across their whole range, so dust cannot scratch them.

Cite this page

AstroHot. “Cancer Birthstone: Ruby and Moonstone and What They Mean.” Accessed October 27, 2026. https://astrohot.com/birthstones/by-zodiac/cancer/

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