01
Recutting Service
We recut existing diamonds to higher cut grades — and even improve colour — with minimal weight loss, earning the trust of top jewelers worldwide.
Est. 1994 · Tokyo, Japan
30 Years
of Trust
World's highest-value diamond polishing technology.
The value of a diamond is determined by its polish.
Consistently achieving Triple Excellent · 3EX
- 30Years of trust
- 3EXAchievement of 3EX
- 20×More refined polish
- 200×Magnification, no marks
The 3EX standard
Consistently achieving Triple Excellent.
Recognised as the highest standard for polish precision. Our polish is up to 20× more refined — transforming the very nature of light reflection. Even under 200× magnification, no polishing marks are visible.
Learn moreSpecial services by diamond experts
Services only diamond
experts can provide.
02
Original Cutting Service
From Sakura, Ume and Lotus designs inspired by Japanese aesthetics to fully custom cuts, we bring extraordinary light and ideas to life.
03
Brand Development
We support everything from sourcing and design to brand concept and market launch — building meaningful brands that maximise the value of diamonds.
Original cutting
Cuts inspired by
Japanese aesthetics.
Light-performance engineering meets the spirit of Sakura, Ume and Lotus — diamond cuts that exist nowhere else.
Commission a cutCraftsmen's introduction
Exceptional craftsmen backed
by 30 years of trust.
Masaru Sekine
Master Diamond Polisher
A one-of-a-kind master with over 30 years of experience — the only Japanese craftsman capable of handling the entire process, from rough selection to final polish.
Thailand Factory Team
World-Class Polishing Team
Built on 30 years of Japanese polishing philosophy and trained directly by Japanese experts, our team achieves brilliance that exceeds even 3EX.
Yasuka Kitayama
Brand Development Specialist
With 20+ years in jewelry design and brand management, she transforms ideas into value and elevates the true worth of diamond jewelry.
What makes our diamonds special
The spirit of Japanese craftsmanship in every step.
Three disciplines that set EIWA polish apart from the global standard.
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01100% achievement of 3EX
Through direct training in our Thailand factory, every team member consistently achieves 3EX.
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02Beyond 3EX — our standard
We evaluate Reflection and Surface independently. Our polish is 10–20× more refined, enhancing both the quantity and quality of light.
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03The Japanese philosophy
“God resides in the details.” Our refusal to settle for good enough creates perfection that cannot be replicated.
Our partner companies
Trusted by the world's
diamond institutions.
EIWA Factory Co., Ltd.
The core diamond polishing facility in Thailand that embodies EIWA Material's philosophy and quality standards — consistently achieving Triple Excellent.
Malca-Amit Japan
A global leader in high-security logistics for valuable assets — ensuring safe, secure transport of diamonds and fine jewelry to world-class standards.
“God resides
The philosophy embedded in every EIWA polish
in the details.”
Beyond the global standard
Quality that exceeds
world standards.
- 200×
Zero polishing marks
Even under 200× magnification, our surfaces remain flawless.
- 10–20×
More light return
Reflection and surface refined far beyond traditional cut grading.
- 3EX+
Our unique standard
We hold every stone to a bar that exceeds Triple Excellent.
Contact us
Entrust your diamonds to us.
- By phone
- 03-6381-7541
- By email
- info@eiwa-material.com
- After-sales
- Comprehensive support — our commitment continues long after delivery.
