What is sapphire glass?

Glass...or sapphire? Why not both! Sapphire glass is used in the best timepieces ever, thanks to its transparency and its great resistance. Let's find out together what sapphire glass is.

A little background…

It is a resistant and hard material, very prestigious. It is formed, in fact, by sapphire, or rather by Corundum , a mineral made of aluminum oxide. We usually find it in jewelry, with its gems of the most varied colors. It is important to remember, however, that the different shades are the result of the presence of impurities, such as hematite or rutile. Sapphire/corundum in its natural state is in fact transparent.

There is also synthetic sapphire, thanks to the creation of the French chemist Auguste Verneuil, who lived between the mid-1800s and the beginning of the 1900s.

What to choose?

As we have seen, sapphire glass is usually chosen for luxury timepieces. However, it is not the only material used for watches. Let's see the alternatives

Acrylic

It is the cheapest material, but also the most prone to scratches. A positive aspect of acrylic is that it can be polished very easily. It has a high resistance to shock and pressure. Compared to glass, it does not shatter. It is preferable in sports watches or those that require great resistance.

Mineral glass

It is, in fact, a traditional glass that undergoes a chemical treatment to improve scratch resistance. It has a low cost, although higher than acrylic. It is a real middle ground between the other two materials.

Sapphire glass

Definitely the best for scratch resistance and strength, it is difficult to crack due to impacts. Unfortunately, the downside is that, if it suffers a strong impact, it tends to break. It is more expensive than the other two materials.

It has a higher hardness than mineral glass and, on the Mohs scale, which evaluates the hardness of materials, it is second only to diamond. It can therefore be scratched only by diamond.

A curiosity

Although it is difficult to trace the history of the use of sapphire crystal in watchmaking, it seems that around 1930 it was used by Jeager-LeCoultre on some Reverso models, very popular watches. From the 60s, it became more famous for the first Rolex with sapphire crystal: these are the Perpetual date ref 1530, Perpetual Datejust ref 1630 and Oysterquartz.

Since the mid-90s, sapphire crystal has been the crystal of choice for Rolex, in all new watches. Today, the brand also treats it with anti-scratch and anti-reflective coatings, to make the dial of its watches perfect in every detail.

It is therefore the material preferred by the best brands, thanks to its resistance. It protects what it covers, ensuring its visibility. A true jewel of watchmaking, all to be discovered.