Kagamiiwa - Shinshiro

Mirror rocks consist of pitchstones or dacite megaliths. Pitchstone is a black, glassy obsidian-like stone, but originates from the homogeneous magma of common white granite and rhyolite. Pitchstone and its origin Pitchstone originates from lava of the same quality as rhyolite and granite, and is a volcanic rock containing 5 to 10% of water. Granite and rhyolite have almost no water, but the water was separated during the cooling and solidification process. Magma basically contains a large amount of water (about 5% of its weight) in the process of its development. Pitchstone is a rhyolite lava that is cooled in a very short time and solidified without water separation. There is a theory that. The large amount of water separated from the lava is the source of the deposit and is also the pyroclastic flow of that dreaded hot steam. Why does magma contain so much water? This is because a large amount of water is indispensable for the generation of magma. Everyone knows that Japanese magma can be created by the friction of the subduction of the oceanic plate, but in fact, the heat of friction alone is not enough to generate magma, and a large amount of water carried by the oceanic plate is used to generate magma. Is essential. In an underground high-pressure environment, the melting point of rocks is lowered by the water carried to the oceanic crust, and a phenomenon of high-temperature rock hydrolysis occurs around 150 km underground. This is the origin of Japanese magma. The abundant water in this magma later turns into a deposit. A large amount of water in the lava dissolves rare earths such as precious metals in the lava and separates them at the time of rock formation, creating gaps in the rock and accumulating various abundant minerals such as gold in the gaps. This is why there are various deposits such as Tsugukinzan around Mt. Horaiji. It is also a source of abundant hot springs. All the special geological features around Mt. Horaiji originate from the large-scale caldera eruption of Shitara volcano 15 million years ago.