A blue rock discovered in Itoigawa City, Niigata Prefecture, was confirmed to be the gemstone lapis lazuli, marking the first confirmed occurrence of the mineral in Japan.
Itoigawa lies at the northern edge of the Fossa Magna, a major fault zone that divides the Japanese archipelago into eastern and western regions. The area is already well known for its jadeite (hard jade) deposits.
The presence of both lapis lazuli and jadeite in the same region is considered a world-first discovery and may offer new insights into the area’s unusually complex geology.
Lapis lazuli is a deep blue metamorphic rock prized for its vivid color. Its powdered form has been used for more than 7,000 years as the pigment ultramarine, once so valuable it was sometimes worth more than gold. It is said to have been used as eyeshadow by Cleopatra, the last queen of ancient Egypt. In early modern Europe, the Dutch painter Johannes Vermeer also used it, including in works such as Girl with a Pearl Earring, notably in elements like the subject’s turban.
High-quality lapis lazuli has historically been found in only a few regions worldwide, most notably northeastern Afghanistan. Therefore, specimens discovered in ancient sites across the Ancient Near East, China, Greece, and Rome—as well as treasures in the Shosoin Repository at Todai-ji Temple in Nara Prefecture—are generally believed to have originated from Afghan sources.
Mislabeled Rocks
The Itoigawa lapis lazuli was identified from rocks collected in the city by two jadeite enthusiasts. After the specimens were brought to a local jade and mineral shop, they were analyzed through chemical composition testing and X-ray diffraction by Professor Emeritus Satoshi Matsubara of the National Museum of Nature and Science, who confirmed they were lapis lazuli.
Koichi Monma, a principal research scientist at the museum involved in the analysis, pointed to two key reasons supporting the identification. First, similar rocks had been independently collected by two people at nearly the same location but at different times, strengthening the credibility of the find. Second, the mineral composition matched that of lapis lazuli, including minerals such as hauyne, which gives the stone its deep blue color, and sodalite. This composition clearly differs from well-known sources such as Afghanistan and Chile.
Lapis lazuli from Itoigawa (left) is lighter in color than that from Afghanistan (right), March 26, Tsukuba, Ibaraki Prefecture. (©Sankei/Hikaru Ichinosawa)
Geological Significance
Until now, blue rocks found in Itoigawa were generally identified as dumortierite. The newly recognized lapis lazuli had also been sold under that name at the same shop when Matsubara visited in 2025. However, he noticed something unusual under magnification and brought a sample back for further study, leading to the discovery.
Reflecting on the finding, Monma said, “My first impression was, ‘Could it really come from Itoigawa?’ I had always assumed that lapis lazuli does not exist in Japan.”
Itoigawa is already known as Japan’s primary source of jadeite, the national stone. Jadeite is thought to have been brought from deep underground by tectonic activity, along with other rocks. Lapis lazuli is believed to have reached the surface through a similar process, although the exact mechanism remains unclear.
Koichi Monma led the chemical analysis of the rocks. March 26, Tsukuba, Ibaraki Prefecture. (©Sankei/Hikaru Ichinosawa)
Monma noted, “We never expected lapis lazuli to appear in this region. It has become clear that Itoigawa has unexpectedly complex geological phenomena and an extremely complicated geology.”
Further research will examine the conditions under which the lapis lazuli formed and how it was transported to the surface.
He also said public interest exceeded expectations. After the announcement, several people came forward reporting that they had previously found what they believed to be lapis lazuli in the area.
There have even been suggestions that corundum, the mineral group that includes ruby, may also exist in Itoigawa. While the region’s deep geological structure is still not fully understood, it is now clear that both jadeite and lapis lazuli can be found near the surface, highlighting the area’s unusually complex geology.
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(Read the article in Japanese.)
Author: Hikaru Ichinosawa, The Sankei Shimbun
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