From Japan · Updated 2026-07-03
Kyoto natural whetstones, explained by the people who mine them
The strata are ~250 million years old; the stamps on the stones are layer names, not marketing. Sourced from an active Kameoka mining family and the Natural Whetstone Museum.
Where the stones come from
According to materials from the Natural Whetstone Museum in Kameoka (Kyoto), the strata that yield Kyoto finishing stones formed roughly 250 million years ago: volcanic ash and clay settling on the deep Pacific seabed at about one millimeter per thousand years, carried north on the Philippine plate, and uplifted around present-day Kameoka.
Reading the stamps: layers, not brands
Totoriya, a family operation still quarrying Maruoyama in Kameoka, grades its stones by geological layer — shiki-suita (敷巣板), awasa (合さ), tomae (戸前), senmai (千枚), hachimai (八枚), uchigumori (内曇) and more, around 30 grades distinguished by color and pattern. The ink stamps on a natural stone are these layer and grade marks. If you own a stamped awasedo, the stamp is telling you which stratum it was cut from.
Museum-grade awasedo from the famous Nakayama mine — whose output peaked in the late 1940s and 1950s — are preserved at the Kameoka museum.
Sources: 砥取家 — 丸尾山の天然砥石 (Totoriya: Maruoyama natural stones) · 天然砥石館 (Natural Whetstone Museum, Kameoka)
These summaries extract facts from Japanese primary sources and rewrite them in our own words, with attribution. For the full detail (and the original nuance), follow the source links — they deserve the traffic.