Casio Put Two Blue Sapphires Into This 500-Piece G-Shock

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The MRG-B5000SA-2 puts two 2-carat lab-grown blue sapphires into the bezel of a shock-resistant square G-Shock. Casio surrounds them with a multi-part metal structure rather than building the case from sapphire, a crucial distinction from its separate MRG-D5000 Blue Sapphire. Production is limited to 500 individually numbered watches worldwide.

Price: TBD
Where to Buy: Casio

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Two sapphires, each weighing 2 carats, provide the centerpiece

Casio says the MRG-B5000SA takes inspiration from the intense blue appearance of ice caves found in Iceland’s largest glacier. That connection is the company’s design story rather than a functional characteristic of the watch.

Casio uses two lab-grown blue sapphire gemstones, each weighing 2 carats, in the bezel. Each receives an original eight-facet cut inspired by the G-Shock form before being polished.

Casio says the sapphires are grown as ingots over several months, after which sections are selected for color consistency, clarity, and minimal inclusions. The company says lab-grown sapphire allows a degree of quality control that would be difficult to achieve with natural gemstones.

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This is not the MRG-D5000 Blue Sapphire

Casio lists two distinct blue-sapphire MR-G anniversary models: the 500-piece MRG-B5000SA and the 20-piece MRG-D5000.

The MRG-B5000SA-2 Super Blue remains based on the MRG-B5000 platform. Its two blue sapphire gemstones are incorporated into a bezel structure otherwise built around specialty metals and shock-absorbing components.

The MRG-D5000 Blue Sapphire goes considerably further. It uses an entirely blue-sapphire bezel and a screwless, multi-component case-and-bezel structure designed to protect the sapphire. Casio lists titanium and sapphire crystal as its case and bezel materials, so this does not mean every case component is sapphire. Casio calls the D5000 its first MR-G crafted directly in sapphire crystal, and production is limited to just 20 pieces worldwide.

The MRG-B5000SA therefore should not be described as a sapphire-cased version of the MRG-B5000. Sapphire gemstones are prominent parts of its design, but the surrounding structure remains heavily dependent on metal.

COBARION and Ti64 surround the sapphires

Casio uses COBARION for the top bezel, while the side bezels, case, caseback, buttons, and buckle employ Ti64 titanium.

According to Casio, COBARION is approximately four times harder than pure titanium, while its Ti64 alloy is approximately twice as hard as pure titanium. Casio also compares COBARION’s appearance to the shine of platinum.

Those hardness and appearance comparisons are manufacturer claims rather than independent durability testing of the finished MRG-B5000SA.

What can be established is Casio’s material strategy. Instead of conventional titanium throughout the exterior, it uses different high-hardness alloys for specific components surrounding the sapphire gemstones.

Protecting the gemstones required its own structure

Putting exposed gemstones into a G-Shock bezel creates an obvious engineering challenge: they still need to coexist with the watch’s shock-resistant construction.

Casio developed a dedicated version of its Multi-Guard Structure for the MRG-B5000SA. The bezel consists of multiple separate components rather than one piece, with metal and shock-absorbing parts working together around the watch.

Casio specifically says αGEL protects the blue sapphire gemstones, while suspension components at the four corners and silicone buffers help absorb impacts to the module. The completed watch is officially specified as shock resistant.

That does not make its sapphire components impossible to chip or damage. Casio’s documentation establishes the protective engineering and shock-resistant rating, not immunity from every type of impact.

Blue extends beyond the gemstones

The sapphire inserts are only part of the Super Blue treatment. Casio applies blue arc ion plating to the bezel, blue ion plating to the four-corner suspension components, and blue vapor deposition to the sapphire watch crystal. The result uses several blue treatments rather than relying solely on the two gemstones for color.

The display itself is protected by sapphire crystal with an anti-reflective coating.

Casio pairs the watch with a Dura Soft fluoro-rubber band and tight-lock, one-press, three-fold clasp. The clasp also incorporates high-hardness materials including Ti64 titanium.

Underneath, this is still a functional MRG-B5000

The MRG-B5000SA measures 49.4 × 43.2 × 12.9mm and weighs 103 grams. Casio rates it for 200 meters of water resistance.

Its unusual materials have not displaced the familiar modern G-Shock technology underneath.

Tough Solar provides power, while Multiband 6 radio reception and Bluetooth Smartphone Link provide automatic time adjustment. Casio also includes World Time, a stopwatch, countdown timer, five daily alarms, full auto-calendar, and Super Illuminator LED backlight.

Casio estimates approximately 10 months of operation after a full charge without further light exposure under normal use, extending to about 22 months when stored in darkness with power saving active.

The caseback carries the MR-G 30TH anniversary logo and an individual serial number, while Casio supplies the watch in special anniversary packaging.

Price: TBD
Where to Buy: Casio

What makes this MR-G different?

The MRG-B5000SA-2 adds a jewelry-like centerpiece to the familiar square MR-G platform without displacing its solar-powered timekeeping and digital functions. Its distinctive feature is the engineering that accommodates two blue sapphires within a shock-resistant metal watch.

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