2023.12.19 Jewellery Column

A diamond for two created from a single gemstone


 "ith Diamonds" is ith's special program that provides customers with two pieces of diamonds cut from the same rough diamond. The rough diamonds are mined in the same location, cut and polished into a pair of diamonds using special inspection and processing techniques, and then set into rings for the couple.


Until the diamond reaches us

In order to gain a better understanding of the 'ith Diamonds', we would like to briefly explain how diamonds are distributed and how they reach us.

Rough diamonds are mined in diamond mines in their native regions, such as South Africa, Canada, and Russia. The photo shows the Mir mine in Russia, one of the largest mines in the world. This mine accounts for the majority of Russia's diamond production.

Rough diamonds mined at these mines are sent to processing plants through site holders and markets that have been given the right to receive supply from rough diamond sales companies, where they undergo various inspections before being cut and polished to enhance their commercial value as diamonds for jewellery.

The world's largest diamond hub has historically been India, the center of diamond trading. Even today, more than 95% of the world's diamonds are cut in India. From there, diamonds pass through exchanges around the world and are distributed to various regions.

Through this process, diamonds purchased by Japanese wholesalers and Indian businesses are distributed in Japan and delivered to us.

Two diamonds cut from one rough gemstone

In the normal process, diamonds are cut into pieces in order to extract as many diamonds as possible from a single rough diamond (that can be handled as a product) as efficiently as possible, and then sorted by quality and size. However, the diamonds handled by "ith Diamonds" are cut generously to produce a pair of diamonds from a single rough diamond, without pursuing efficiency.

At the same time, diamonds are carefully managed by assigning unique numbers and separating the cleaning process to ensure that the combination of diamonds does not get mixed up in each process. Through this thoroughly controlled process, diamonds with special stories are created.

Two diamonds born from the same gemstone will shine in each other's rings. These are truly one-of-a-kind diamonds that are perfect for a wedding ring that is unique to the couple.

Diamond Traceability

There is another important aspect to the " ith Diamonds" initiative. It is the traceability of diamonds.

In the world of diamond jewellery, the issue of synthetic and second-hand diamonds is currently brought to public attention. In 2019, Tiffany & Co., one of the world's leading jewellery brands, initiated a program to disclose the origin information of diamonds, increasing its attention within and outside the industry.


Neither synthetic diamonds nor second-hand diamonds have any problems of their own, but the fact that they are mixed together without proof and cannot be distinguished from each other is said to be a major problem.

It's becoming a reality that what was believed and purchased as natural diamonds are actually synthetic diamonds.

We position " ith Diamonds " as an initiative to address this issue of traceability, while at the same time focusing on a beautiful story.


In order to identify each diamond, we collect and store the Kimberley Process Certificate, which is proof of origin, photographs of the rough diamond, and SARINE data, which is a blueprint of the diamond that is cut from the rough. Through these, we have built a system that allows us to trace the path of the diamond from its place of origin through processing to sales and distribution.


In addition, the final processing of the diamonds to be set in the customer's ring is done exclusively in our own workshop. In this way, the possibility of mix-ups and misplaced diamonds is thoroughly eliminated.

Customers who choose ith Diamonds are issued with an ith original certificate as proof that they have gone through these processes.

Our commitment to creating value

Although ith started out as a small atelier, we have continued to grow thanks to the support of many customers and stakeholders. We would like to continue to make efforts one by one so that we can create and deliver even higher value to the many customers and visitors who have come to our atelier with high expectations of our work.

We hope that " ith Diamonds" will be one of the ways to create happiness and value in the world.


ith Director: Yoshida




A diamond for two created from a single gemstone