Yaginoshima Asagi Whetstone 6" x 1"

Japanese name (Kanji): 八木ノ嶋 浅黄 (also written: 八木嶋, 八木の嶋)

Name breakdown:

• 八木ノ嶋 (Yaginoshima) — a western Kyoto mine (Nishi Mono) in the Tamba/Tanba region, located east of Ohira and north of Kouzaki. Historically controlled by Akechi Mitsuhide. The mine has been closed for a long time.
• 浅黄 (Asagi) — visual/color attribute: deep dark blue to grey-blue coloration, often with holographic Suminagashi-like patterns. Asagi is a color descriptor only; hardness is not implied by color. Strata is not explicitly named in this combination but Yaginoshima Asagi is associated with the Hon-Kuchi Naori seam.

Mining region: Western mine (Nishi Mono), Tamba/Tanba area, Kyoto Prefecture. Yaginoshima is connected to the main Hon-Kuchi Naori geological seam, which runs from Maruoyama/Ouchi/Yaginoshima eastward across the Katsura River toward Ohira, Ozuku, Okudo, Nakayama, and Narutaki. Suita from Yaginoshima is most famous, along with its Namito stones. The mine is permanently closed.

Grit rating (JIS equivalent): Yaginoshima stones span a wide range depending on hardness. Softer specimens (Aoto-type, LV 2–3) are documented at approximately 4,000–6,000 JIS. Hard Asagi specimens (LV 4.5–5) are extremely dense and fine, suitable for razor finishing, placing them at approximately 10,000–12,000 JIS. The Asagi variant specifically is characterized as extremely dense and fine.

LV Hardness: LV 5 (very hard) for the dense Asagi type. Confirmed at hardness 5 across multiple vendor listings for Yaginoshima Asagi. Some specimens rated LV 2–4 exist (the mine produces a range), but the Asagi type from this mine is specifically known for exceptional hardness and density. On the 1–5 Tanaka Toishi scale: hardness 4.5, wear rate 1.5, self-slurry 1.5.

Recommended progression: After a synthetic 5,000–8,000 JIS stone or a medium JNAT (LV 2–3). For razor use, a full Mikawa Shiro Nagura progression (Botan → Mejiro → Koma) is recommended before or on this stone. Also highly effective for knives and traditional carpentry tools as a final finishing step.

Composition: High-density siliceous shale, Hon-Kuchi Naori geological formation. Characteristic deep dark blue-grey base coloration with holographic Suminagashi-like patterning and Goma (sesame seed) inclusions. The very high density of the stone is responsible for both its hardness and exceptional fineness.

Steels to sharpen: Universal, with particular strength in razor finishing. Despite LV 5 hardness, demonstrates smooth sharpening behavior and works well with heavier blades such as knives and woodworking tools. Produces a very even and consistent Kasumi finish. Respected in traditional Japanese carpentry for tool finishing. Well suited to high-carbon steels; use with slurry for soft iron cladding.

Usage recommendations:

• No soaking required — surface wetting only
• At LV 5, self-slurry production is low (rated 1.5/5); use a nagura to raise slurry — Mikawa Shiro Nagura progression is strongly recommended for razors
• Stone translates nagura feedback exceptionally well, giving clear indication of edge development
• Despite high hardness, demonstrates surprisingly smooth and manageable behavior even on heavier blades
• Goma (black sesame-seed dots) present — test for toxicity before honing fine edges; hard Goma can scratch soft jigane if used without slurry, but are safe with slurry in place
• Seal sides and base with cashew lacquer; do not soak
• Offers exceptional performance-to-price value in the super-hard stone category