Natural Stones

We love natural stones—so much so that our name, Strata, was inspired by how a Japanese natural stone (tennen toishi) develops its physical and aesthetic characteristics based on the stratum from which it is quarried (along with other factors like specific mines, geographic origin, etc.). The variety of natural stones in Japan, let alone the world, is vast. Each stone has its own unique “character,” interacting differently with various steels, construction types, and tasks—whether for polishing, sharpening, repairing, or beyond. Natural stones offer results that even today’s synthetic stones cannot fully replicate, making them highly valued in the polishing and sharpening world.

Because we are so passionate about natural stones, we take them very seriously. We source only from trusted connections who provide consistently high-quality stones. We do our best to test each stone stone using a simple evaluation scale, along with a brief summary of its characteristics and ideal use cases. However, these assessments are subjective and may differ from your own experience—just as each stone’s appearance will vary. Our reviews are meant to provide a general sense of a stone, not an exact prediction of how it will perform for you.

Natural Stones vs. Synthetic Stones

Natural stones tend to be more “abstract” compared to synthetic stones, which are highly consistent, designed for speed and efficiency, widely available, and often more affordable. We strongly recommend starting your sharpening journey with synthetic stones before transitioning to natural ones. Synthetic stones provide a much more stable reference point for understanding sharpening fundamentals, making it easier to compare and navigate the more varied and “organic” nature of natural stones. With practice and study, however, you can develop a strong understanding of how a natural stone will likely perform and behave.

By “abstract,” we mean that natural stones, unlike the vast majority of synthetic stones, do not have a set, uniform grit—they are formed by nature, not manufactured. Additionally, in most Japanese natural stones, the abrasive particles are friable, meaning they break down into finer and finer bits as you work. This not only makes their initial grit range difficult to compare to a synthetic stone but also means that the effective grit and rate of work evolve during use. Having a solid grasp of synthetic grit ratings (e.g., 1000, 3000, etc.) can help guide you toward understanding the general grit range of a natural stone. Even this foundational knowledge, however, only scratches the surface of what makes natural stones so fascinating—it is an endlessly engaging and rewarding subject.

Because natural stones require physically demanding and often dangerous labor to extract, they are inherently more expensive. Almost all mines in Japan are either permanently closed or operate on a very limited basis, extracting small amounts of material at a time. This results in low supply and high global demand. Natural stones are not only essential for traditional Japanese crafts such as sword polishing and woodworking but are also irreplaceable for certain applications where no synthetic alternative can achieve the same results. This makes some stones extremely sought after—and extremely expensive. That said, some stones are more abundant, easier to mine, have lesser demand, or are suited for more limited use cases, all of which contribute to a lower price point. While high-end stones can cost hundreds to thousands of dollars, there are also more affordable options if you’re just starting your journey into the world of natural stones.

If you have questions about our stones—or natural stones in general—please don’t hesitate to reach out. Have fun!