Mitake no Kagami-iwa (Mirror Rock of Mitake), located in Kamikawa-machi, Kodama-gun, Saitama Prefecture, is a precious geological site designated as a Special Natural Monument of Japan. It showcases the traces of a rock fault from approximately 100 million years ago. The friction generated when the fault plane shifted polished the rock surface to a mirror-like sheen, creating one of Japan's largest fault mirror planes.
The rock face is impressively large, measuring approximately 4 meters in height and 9 meters in width, with a northward tilt of about 30 degrees. Composed of reddish-brown quartzite schist, its surface gleams with a luster produced by intense friction, displaying striations indicating the direction of the rock's movement.
This Mirror Rock is mentioned in Edo-period writings like "Yureki Zaki" and "Koshi Yawata," indicating its long-standing recognition. The area surrounding Mount Mitake, where the rock is located, is also known for the ruins of Mitake Castle, a medieval mountain fortress. Legend says the reddish-brown color is from being smoked with torches to prevent it from being a target for enemies, or that it reflected the flames of a fire during the fall of Takasaki Castle (Gunma Prefecture). This reflective quality is believed to be the origin of its name, "Mirror Rock."
Mitake no Kagami-iwa is a precious tourist spot where history and nature intertwine. When you visit, immerse yourself in the beauty of the Mirror Rock while contemplating the magnificent history of tectonic activity.
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