At SARAH & SEBASTIAN, natural diamonds are central to our design language; celebrated not just for their beauty, but for their origins, structure and symbolism. Whether you’re deep in the engagement ring search or simply curious, here are five things you might not know about these extraordinary stones.

1. They're billions of years old

Most natural diamonds are between 1 and 3 billion years old, formed deep within the Earth’s mantle under intense heat and pressure. For Creative Director and gemologist Sarah Munro, their age is part of the fascination: “Their ancient origins, shaped by Earth’s transformative forces, always blow my mind.”

Each stone is essentially a geological time capsule—carbon transformed by nature and delivered to the surface through volcanic eruptions. If that’s not awe-inspiring, we don’t know what is.

2. Inclusions aren’t imperfections—they’re stories

Look closely into a diamond, and you may see what gemologists call “inclusions”—tiny internal markings that occur during formation. These aren’t flaws; they’re proof of the diamond’s natural journey.

“The micro-inclusions found within diamonds tell unique stories about our Earth’s ancient history,” explains our in-house diamond expert, Crissabella Sacco. They’re also part of what makes each stone completely unique.

3. Cut is everything

Yes, carat matters, but a diamond’s cut is what brings it to life. The way a stone is shaped, polished and proportioned directly impacts how it reflects light—its brilliance, fire, and that unmistakable sparkle.

“I strongly believe that cut is the most important element,” Crissabella adds. At SARAH & SEBASTIAN, we only work with Excellent to Very Good cut diamonds, and for round brilliants, we exclusively source Triple Excellent.

4. The rarest diamonds aren’t necessarily the biggest

It’s a common misconception that bigger means better. In truth, the rarest and most valuable natural diamonds are those with near-perfect clarity and minimal colour—what gemologists call D to H on the colour scale and FL to VS2 in clarity.

And while flawless diamonds are exceptional, many of our clients fall in love with stones that show a trace of individuality—something a little off-centre, a little unexpected.

5. There's a fifth C you should always ask about

Beyond the traditional four Cs (cut, colour, clarity, and carat), there’s a crucial fifth: certification. Always ensure your diamond comes with an independent grading report, such as one from the Gemological Institute of America (GIA). This guarantees transparency, ethical sourcing, and peace of mind.

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A final note: they’re April’s birthstone

Derived from the Greek word adamas, meaning ‘invincible, ’ diamonds have long symbolised strength, clarity and enduring love. As the traditional birthstone for April, diamond jewellery makes a powerful, personal gift—whether for a loved one or as an ode to self.

Explore our natural diamond collection or book an appointment with a SARAH & SEBASTIAN diamond specialist to begin your engagement journey.

Read our deep dive into the world of natural diamonds here.