Sapphire Crystal: The Ultimate Transparent Protection for High Watchmaking

Sapphire crystal is the definitive material for protecting the heart of a timepiece. Often referred to as sapphire glass, this transparent shield is far more than ordinary glass—it is a pure crystal, composed of the same mineral structure as natural sapphire gemstones. Unlike mined sapphires, however, sapphire crystal used in watchmaking is synthetically produced to achieve the highest level of purity, ensuring absolute transparency. This clarity allows for an unobstructed view of the watch’s dial while offering the highest level of durability.

The Evolution of Sapphire Crystal in Watchmaking

For centuries, watch crystals were made from standard window-quality glass and later, various types of hardened plastics known as mineral crystal. While functional, these materials were prone to scratching and shattering, limiting their effectiveness in protecting fine timepieces.

The turning point came in the 1970s when advancements in synthetic sapphire production made the material more accessible. By the mid-1990s, sapphire crystal had overwhelmingly replaced mineral crystal in high-end watchmaking. Today, it is the gold standard, ensuring that luxury timepieces maintain pristine legibility and resilience against everyday wear.

Unrivaled Hardness: The Protective Power of Sapphire Crystal

Sapphire crystal is celebrated not only for its flawless transparency but also for its extraordinary hardness. Its scratch resistance is quantified using the Mohs scale of mineral hardness, which ranks materials from 1 to 10—diamond being the hardest at 10, and sapphire closely following at 9. This means that only another sapphire or a diamond can scratch a sapphire crystal, making it the perfect material to maintain a watch’s immaculate appearance over time.

However, while sapphire crystal is highly resistant to scratches, it is not entirely shatter-proof. A strong impact at the right angle and force can break it, though such an occurrence would likely damage the entire watch, including its intricate mechanical movement. Sapphire crystal timepieces are built for durability, but like all fine objects, they require careful handling to preserve their brilliance.

Pushing the Boundaries of Sapphire Crystal Design

At Jacob & Co., sapphire crystal is more than just a protective element—it is an artistic and engineering marvel. Every timepiece in the brand’s collection is fitted with sapphire crystal, but in many cases, this material is taken to new heights of innovation.

Some models, such as the Astronomia Tourbillon, feature high, curved sapphire crystals that provide an expansive view of the intricate movement within. Others, like The Mystery Tourbillon, boast domed sapphire crystals, adding depth and dimensionality to the timepiece’s aesthetic. In the Astronomia Sky, sapphire crystal wraps around the entire case, creating an extraordinary 360-degree transparent showcase of the watch’s complexity.

At its most advanced, Jacob & Co. transforms sapphire crystal into an entire watch case. The Bugatti Chiron Tourbillon Sapphire Crystal and Twin Turbo Furious Sapphire Crystal stand as testaments to this mastery, encasing their groundbreaking mechanical movements within fully transparent sapphire cases. These creations redefine the limits of what is possible in watchmaking, blending exceptional craftsmanship with an ethereal, almost weightless aesthetic.

The Future of Sapphire Crystal in Haute Horology

As watchmaking continues to evolve, sapphire crystal remains at the forefront of innovation. Its perfect fusion of protection, clarity, and artistry ensures that it will always be the material of choice for high watchmaking. Jacob & Co. continues to lead this evolution, using sapphire crystal not just as a functional component but as a defining feature of modern haute horology.

With each new creation, Jacob & Co. proves that sapphire crystal is not merely a shield—it is a window into the artistry, precision, and imagination that define the brand’s unparalleled timepieces.