Watch Glass Replacements: Mineral Glass vs. Sapphire Crystal

The unthinkable just happened: after a minor accident that caused you to ding your Seiko watch, your beloved timepiece’s crowning crystal was cracked beyond repair. And although you may have long feared the possibility of cracking your watch glass, actually witnessing it is something you can never be truly prepared for. With time being of the essence, you rush to get it fixed to avoid exposing your components to harmful elements.

Now that your watch is safely kept away for the meantime, you’re focused on solving your broken glass problem so you can wear your beloved timepiece again. Fortunately, it’s times like these where the internet is your best friend because you can always visit websites that are ready to supply you with the replacement you need (such as Seiko Mods).

After typing your watch model in and clicking search, you’re immediately greeted with dozens of glass replacement options. As you browse through the assortment of listings and read their accompanying descriptions, you will likely find two terms that pique your interest: sapphire and mineral crystal.

Telling Mineral Glass and Sapphire Crystal Apart

The terms “sapphire crystal” and “mineral glass” have become hot topics for those looking to improve or mod their watches. And for those dealing with broken watch glasses, these upgrades are especially attractive because they offer sturdier and more effective alternatives than the original parts.

Seen as the upgrades to standard, factory-issued plastic or acrylic watch glass, both sapphire and crystal materials bear many advantages worth investing in. To give you a better idea of what your money can get you, let’s go over both options: 

Mineral Glass

Commonly used in most mid-range watches (especially in Seiko divers in the same range), mineral glass is considered a durable “starter” upgrade that modders seek when starting their projects.

Mineral glass can be a little more expensive than plastic or acrylic crystals, but the price difference is justified because they are significantly more scratch-resistant. This glass option is rated higher for durability is because of its heat-tempered surface. Through this manufacturing process, mineral glass is much less likely to “splinter” during heavy contact or impact. However, it’s worth noting that if a mineral crystal is scratched or chipped, it must be replaced!

Synthetic Sapphire

In today’s modding and watch manufacturing markets, synthetic sapphire (or “sapphire crystal”, as it’s commonly called) is considered the highest tier of watch glass materials. Widely acclaimed for higher durability ratings and lifetime guarantees upon installation, these upgrades are a worthy investment for those looking to outfit their watches with the best. 

Technically, synthetic sapphire crystal or “glass” is actually not glass at all—it’s a very hard, transparent material made by crystallising pure aluminium oxide at very high temperatures. The resulting “faux-sapphire” develops the same hardness as a natural sapphire gemstone without the colouring agents that give true gems their various hues. 

Using the properties of sapphire crystals, their namesake watch glasses provide unmatched durability with one of the hardest substances on earth. Given that natural sapphire registers as a 9 on the Mohs scale, the “scratch resistant” label associated with these upgrades holds up!

Choosing the Best Watch Glass

As cliche as it sounds, the answer to this question is: it depends.

If you’re looking to save some money while preserving durability, it’s much better to get a mineral glass replacement. However, if you’re looking to invest in dependability in the long-term so that you don’t have to worry about experiencing broken glass issues again, then a sapphire crystal from Seiko Mods is the way to go! 


Dealing with a broken watch glass can make for a rather stressful experience that no timepiece owner, enthusiast, or collector would ever want to deal with. Fortunately, it also provides a silver lining in the form of a better replacement. Through this guide, you’ll be able to determine whether a mineral glass or sapphire crystal replacement is best suited for your needs. 

When it comes to watch glasses and other watch parts, we’re the leading supplier of Seiko mod parts in the UK that offers various products to make any model unique. Bring out your creativity and escape ubiquity in the watchmaking world by visiting our website and ordering mod parts today!

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