Watch Crystal Types: A Beginner’s Guide

The watch crystal is a crucial component that protects the watch face from scratches, impacts, and other external elements. It not only serves a functional purpose but also contributes to the overall aesthetic appeal of a timepiece. With a wide range of crystal types available in the market, it can be challenging to determine which one best suits your needs. This comprehensive guide aims to demystify the world of watch crystals, exploring their types, materials, and factors to consider when choosing the right one for your watch.

Types of Watch Crystals

1. Acrylic Crystals

Acrylic crystal, plexiglass, and hexalite are all names for the same material called Polymethyl methacrylate (PMMA). It is a thermoplastic and is the least expensive type of watch crystal. If you’re on the hunt for an entry-level, low-cost, or kids’ watch, chances are you’ll find an acrylic crystal gracing the face. These crystals are a go-to choice for watch brands looking to keep manufacturing costs down while still delivering a decent level of protection.

Acrylic crystal is rated three out of ten on the Mohs Scale (which measures the hardness and scratch resistance of minerals). Because of its softness, it is easily scratched. However, minor scratches may be buffed out.

One of the standout qualities acrylic is its flexibility and impact resistance. These crystals can bend and flex without shattering, making them ideal for sports watches or timepieces prone to the occasional knock or drop. And if you do happen to scratch or damage an acrylic crystal, replacement is usually a breeze and easy on the wallet.


  • Incredibly affordable, keeping manufacturing costs low
  • Excellent impact resistance and shatter-proof
  • Minor scratches can often be buffed out
  • It is lighter than mineral and sapphire crystals.
  • Can be molded into various shapes, including the classic domed design


  • Prone to scratches due to its relatively soft nature
  • Can develop a hazy appearance over time
  • Not the best choice for dress watches or formal occasions due to its plastic look

2. Mineral Crystal

Mineral crystal is the most commonly used crystal in watches. Often referred to as “hardlex” in watchmaking circles, these crystals are pretty much the same as the crown glasses you’re used to seeing daily, such as in windows, picture frames, and other such items.

The Mohs Scale gives the mineral crystal a rating of 5 out of 10. It can remain clean and clear for a long time if properly cared for. 


  • Offers improved scratch resistance compared to acrylic crystals
  • Cost-effective and still reasonably priced for most budgets
  • Surface-level scratches can often be buffed out 
  • Maintains clarity and visibility over an extended period


  • Less shatter-resistant than acrylic, unable to withstand severe impacts
  • Does not offer the same level of scratch resistance as premium sapphire crystals
  • Can be susceptible to glare and reflections without an anti-reflective coating 

Speaking of coatings, many watchmakers opt to equip their mineral crystals with an AR (anti-reflective) treatment. This clever addition helps minimize light reflection on the watch face, improving visibility and making it easier to read in bright conditions.

3. Sapphire Crystals

Sapphire crystal is the most expensive type of watch crystal that is commonly used in high-end and expensive watches. It is the third hardest mineral on the Mohs scale, with a rating of 9, after diamond and moissanite. This means you don’t need to worry about it getting scratched because it can only be scratched by materials with greater hardness.

It’s worth noting that most watchmakers use synthetic sapphire, created in a lab, rather than natural sapphire, which can be very expensive. Synthetic sapphire has practically the same properties as natural sapphire, so there’s no need to worry. Synthetic blue sapphire was first created in 1911 by a French chemist named Auguste Verneuil. However, it’s important to remember that while the sapphire crystal is scratch-resistant, it is not impact-resistant and can shatter easily if subjected to a heavy impact.


  • Unmatched scratch resistance
  • Exceptional clarity and brilliance, enhancing the watch’s overall look
  • Lends a luxurious, high-end appearance to any timepiece
  • Synthetic production keeps costs more manageable than natural sapphire


  • It is more expensive than acrylic and mineral crystals
  • Although it can handle normal hits, it cannot resist heavy impacts.


4. Hardlex Crystals (Seiko’s Proprietary) 

Hardlex crystals are a type of tempered mineral crystal developed by Seiko in the 1960s. These crystals are formed by heating mineral crystal and then rapidly cooling it, resulting in a material that is much harder and more resistant to scratches and impacts than regular mineral crystal.


  • Excellent durability and impact resistance
  • Highly resistant to scratches
  • Affordable and cost-effective
  • Maintains clarity and visibility over an extended period


  • Not as scratch-resistant as sapphire crystals
  • Limited availability (proprietary to Seiko watches)

5. Flame Fusion Crystals (Invicta’s Proprietary)

Invicta introduced Flame Fusion crystals as a solution to combine the durability of sapphire with the unique properties of mineral crystals. This process involves fusing synthetic sapphire and mineral crystals together using intense heat, creating a crystal that offers exceptional scratch resistance and superior clarity.


  • Excellent scratch resistance (close to sapphire)
  • Superior clarity and brilliance
  • Affordable and cost-effective alternative to pure sapphire crystals
  • Highly durable and resistant to shattering


  • Limited availability (proprietary to Invicta watches)
  • May not offer the same level of scratch resistance as pure sapphire crystals

Choosing the Right Watch Crystal

Are you wondering which type of watch crystal is best for you? The answer to this question depends on your preferences, needs, lifestyle, and usage. For daily use, such as in the workplace, mineral crystal is the best choice. However, if you have a busy lifestyle with a higher risk of breaking your watch crystal, we recommend acrylic crystal as it has high impact resistance. On the other hand, if you’re looking for a watch for special occasions, sapphire is the ideal choice.

Watch crystals can vary significantly in price, with acrylic crystals being the most affordable option and sapphire crystals commanding a higher premium. Determine your budget and prioritize the features that matter most to you, such as scratch resistance, clarity, or durability.


Choosing the right watch crystal is a crucial decision that can impact the longevity, durability, and aesthetic appeal of your timepiece. By understanding the different types of watch crystals, their materials, and their respective advantages and disadvantages, you can make an informed choice that aligns with your needs, preferences, and budget.

Whether you prioritize scratch resistance, shatter resistance, clarity, or affordability, there is a watch crystal material that can meet your requirements. Remember to consider factors such as the watch type, intended usage, lifestyle, and personal preferences when selecting the appropriate crystal.

If you have any questions or experiences to share regarding watch crystals, feel free to leave a comment below. We’d love to hear your thoughts and insights on this fascinating aspect of watchmaking.


What is the difference between natural and synthetic sapphire crystals?

Natural sapphire crystals are mined from the earth, while synthetic sapphire crystals are created in a laboratory setting. Synthetic sapphire has virtually identical properties to natural sapphire but is more affordable for use in watchmaking.

How do I properly clean and maintain my watch crystal?

Use a soft, lint-free cloth and a mild soap solution or specialized crystal cleaner. Avoid abrasives and harsh chemicals, as they can scratch or damage the surface. Handle the watch with care and store it properly when not in use.

How often should I replace my watch crystal?

There’s no set timeframe, as it depends on the crystal type, usage, and level of damage or scratches. Monitor your watch crystal’s condition and consult a professional watchmaker if you notice significant scratches, cracks, or haziness.

Is a more expensive crystal always better?

Not necessarily. While sapphire crystals offer superior scratch resistance, they may not be the best choice for all situations. Factors like budget, intended usage, and personal preferences should also be considered when selecting a watch crystal.

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