Mineral Crystal vs Sapphire Crystal – Differences and Similarities

Mineral Crystal vs Sapphire Crystal watches

While diving into the wide world of watches online and offline as well, many of you fellow watch lovers have encountered the words mineral crystal and sapphire crystal. Reading countless watch specifications makes you wonder what are the differences and similarities between mineral crystal vs sapphire crystal.

They are the most commonly used glasses in the industry of watchmaking, you already knew that. From Seiko to Rolex, and everything in between, almost every watch manufactured is made of either mineral crystal or sapphire crystal.

Mineral Crystal vs Sapphire Crystal

On special occasions, watch brands choose to use other types of glasses for their watches. Acrylic glass, for example, is a cheaper solution and almost as durable as mineral crystal and sapphire crystal. More about Acrylic glass after taking a closer look at mineral crystal vs sapphire crystal properties, differences, and similarities. Read on…

Mineral Crystal Properties

  • The affordable solution used for entry-level as well as affordable-luxury watches
  • Scratches more easily than sapphire crystal
  • In terms of durability, is more resistant to falls, drops, and shocks when compared with sapphire crystal

Sapphire Crystal Properties

  • Relatively more expensive when compared with other watch glass materials
  • It takes effort to scratch the glass
  • In terms of durability, the sapphire crystal breaks easier than mineral crystal

Mineral Crystal vs Sapphire Crystal (Differences and Similarities)

There are several properties that differentiate mineral crystal and sapphire crystal from one another. And the properties are also reflected in the price of the watch. Sapphire crystal watches, for example, are more expensive when compared with mineral crystal watches. And a top-tier watch brand would always pick sapphire (probably genuine, not synthetic for their timepieces).

The reason why sapphire crystal is better than mineral crystal is due to its scratch resistance. In the Mohs scale (rating measure of the relative hardness of different minerals) sapphire measures 9 out of 10, just behind diamond which measures 10. On the other side, we have mineral crystal which scratches easily and can be a pain in the rear, especially if you are a bit careless. The durability scale of mineral crystal glass is 5-6 out of 10. Still, it is a good material that can endure for ages if maintained properly. 

Surprisingly, mineral crystal, even though it can be easily scratched, is more likely to resist falls and drops when compared with sapphire crystal. According to research/experiment from TWCO, it takes more effort to break a mineral crystal than sapphire. 

The durability of both materials was put into test by dropping a steel ball from different heights on a representative crystal until the crystal would break. Calculating the total amount of energy needed to break sapphire crystal and mineral crystal led the experts to a conclusion. 

For a sapphire crystal to break it takes: 800 to 1800×10^-4 NM

For a mineral crystal to break it takes: 1600 to 2100×10^-4 NM

How to tell the difference between Mineral crystal vs Sapphire crystal glass?

Check for the color reflection

Watch crystals and glasses

It is hard to tell the difference between mineral crystal and sapphire crystal with a naked eye. A trained expert would tell the difference as mineral glass reflects a light blue motive and sapphire glass reflects a light pink motive. However, even a watch connoisseur would not be completely convinced without executing the ultimate test. Scratching the glass…

Try scratching the glass

Watch Glass Scratch Test

To perform the test, you don’t need any special skills, tools, or knowledge to define if the glass of the watch is a sapphire crystal or mineral crystal. As mentioned above, mineral glass is more durable to break, however, it scratches easily.

To find out what glass is your watch made of, simply find a stainless-steel knife or screwdriver and start scratching the glass. (Reminding you that this action cannot be undone and the watch glass will stay scratched forever if it is mineral.) And if by any chance the glass is resisting scratches from your stainless-steel tools, it means you have to do with a sapphire crystal glass. It would take a genuine diamond, or applying a lot of force for the sapphire to scratch. 

Other Methods 

But there are also other methods widely used by watch repair shops, watch dealers, or watch authenticators trying to find out the material of the watch glass. See, if you’re purchasing a luxury watch from an unauthorized dealer, you can easily find out if the watch is a replica just by checking the glass material.

Luxury watch brands will always use sapphire crystal, and if by any chance the watch you are purchasing for a genuine luxury timepiece does not have a sapphire crystal glass, most likely it is an imitation. If you are lacking a high standard of support, try these other methods…

Water test

Simply use a drop of water on the watch glass. In the sapphire crystal, the water will stay in the drop shape. If the water flows and spreads, it is more likely mineral crystal. 

Water test sapphire crystal vs mineral crystal

Sound test

This method is widely used by people dealing with watches on a daily basis. To tell the difference between mineral crystal and sapphire crystal you shouldn’t always have to scratch the glass, as mineral crystal watches are valuable too.

For a watch connoisseur, all it takes is to simply tap the glass with its fingernail, and judging by the sound the crystal makes, you can find out if it’s mineral crystal vs sapphire crystal. The sapphire interprets a solid low-toned sound, while the mineral interprets a high-toned sound.

Other types of watch glasses or crystals 

  • Acrylic Glass
  • Hardlex Crystal
  • Domed sapphire crystal
Types of watch glasses

Acrylic Glass

Acrylic crystal AKA Plexiglass is a contoured form of plastic that has been worked to fit the watch case. It is commonly used for low-cost watches (price range 50 to 150 dollars). Its affordability comes with high sensitivity to scratches. Anything sharp will leave a mark. However, due to its softness, Acrylic glass has strong impact resistance. 

Hardlex Crystal

Hardlex Crystal is a hardened mineral crystal used by Seiko. It is more durable than mineral glass albeit not as scratch resistant as sapphire crystal. On some of their best models, (Presage Cocktail Time collection) Seiko used temperature-treated Hardlex crystal, which is more resistant to extreme temperatures. 

Domed Sapphire Crystal

You have probably noticed “Domed Sapphire crystal” on watch specifications online. In case you did not know, domed sapphire crystal is stronger than its flat counterpart as it spreads the force over a greater area to avoid shattering. It also reduces the light reflection, protecting this way, not only the dial but your eyesight too.