Gemmological Association of Japan Refractometer (est.1955~70s)

This early Japanese refractometer was produced by the Gemmological Association of Japan (日本宝石学協会), a small gemological training and instrument-making body active during the formative decades of Japan’s modern gemstone industry. Little survives about the association itself, but instruments bearing its name represent an important transitional period when domestic makers began developing their own gem-testing tools rather than relying on costly imports.

Compact and utilitarian in design, this refractometer reflects the practical needs of jewellers and students during the post-war expansion of Japan’s gem trade. It features a solid metal housing, a fixed-aperture viewing system, and a glass hemicylinder for refractive-index measurement—the cornerstone test of classical gemology. The serial marking indicates limited-scale production, typical of independent optical workshops of the era. The range of measurement is only between RI=1.50~1.81, with the scale beyond 1.81 was darkened by felt pen ink or some sort. 

Although the association that produced this instrument is no longer active, tools like this refractometer document an early chapter in Japanese gemological education. They illustrate the shift from imported scientific equipment to locally engineered solutions, marking the emergence of Japan’s own gem-testing tradition that later evolved into the professional laboratories and academic societies operating today.

This is a museum archives and no unit is available for sale at this moment.