Granite and Tokyo Tour Series 2025 No.3 National Diet Building

Japan’s National Diet Building and Japanese Granite — A Showcase of Domestic Stone

Field Notes: September 2025

I visited Tokyo in September 2025. Due to heavy rain I didn’t get off the bus, but even under a gray sky the National Diet Building’s facade clearly showed a gentle, pink hue. The soft tone conveyed the texture and dignity unique to granite, adding a calm splendor to the entire structure.

Overview

Completed in 1936, the National Diet Building was designed with a clear policy: use domestic materials wherever possible. As a result, granites from across Japan were selected by use and finish, turning the building into a living “exhibition of Japanese granite.”

What Creates the Pink Facade

The subtle pink seen on the exterior is not Mannari Granite. The hue mainly comes from Giin-ishi (a pink-toned granite quarried on Kurahashi Island, Hiroshima) combined with other domestic stones. Key exterior stones include:

• Giin-ishi (Kurahashi Island, Hiroshima): Pink (“sakura”) granite widely used on upper exterior walls, giving the facade its faint rosy tone.
• Tokuyama Granite (Kurokami Island, Yamaguchi): Durable exterior stone used on parts of the walls and base courses.

Interior & Other Domestic Granites

Inside the building, multiple Japanese granites are allocated by function and finish:

• Mannari Granite (Okayama): Pink granite used in interior elements (e.g., stairs, trims) for a refined, warm look.
• Aji Stone (Kagawa): Ultra-fine granite suited to precision carving at entrances and sculptural details.
• Inada Granite (Ibaraki): Light-toned granite used on walls and floors to convey clarity and solemnity.
• Oshima Granite (Ehime), Inai Stone (Miyagi), and others appear in limited areas, representing a nationwide selection.

Why Granite Was Chosen

1. Durability & Strength: High compressive strength and weather resistance for long-term public use.
2. Workability: Fine-grained domestic granites allow precise carving, polishing, and varied finishes.
3. Symbolism: Using domestic stone demonstrated Japan’s resources and craftsmanship at a national symbol.

Cultural Significance

Beyond politics, the National Diet Building is a convergence of architecture, geology, and craft. Walking its halls reveals shifting colors and textures of different granites—an education in Japanese stone within a single landmark.

At a Glance

Related Reading

• Giin-ishi (Kurahashi Island) — Origins and Characteristics
• Mannari Granite — The Pink Granite of Okayama
• Aji Stone — Japan’s Ultra-Fine Sculpture Granite
• Oshima Granite — Quarries & Architectural Heritage