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From Gifu! Hot Spring Museum Episode 7: Ore Deposits Formed by Hot Water (Hot Springs)

The hot water, which is separated from underground magma and reaches several hundred degrees Celsius, contains various elements such as sodium, potassium, barium, strontium, chlorine, fluorine, tungsten, gold, silver, copper, iron, lead, zinc, tin, and nickel.
This hot water (hot spring water) moves upwards through cracks and faults in underground rocks. As the temperature decreases along the way, it becomes supersaturated, precipitating various minerals such as quartz, native gold, native silver, and native copper in the cracks along the path.

Native gold formed by hot water (from the USA) Owned by Gero Hot Spring Museum

Some of the hot water erupts from the seabed, and when it is cooled by seawater, elements such as sulfur, zinc, lead, iron, and copper in the hot water become supersaturated, precipitating sulfide minerals such as sphalerite, galena, pyrite, and chalcopyrite. Such ore deposits formed by precipitates from magma-originated hot water are called hydrothermal ore deposits.
Due to hydrothermal activity on the seabed, manganese and iron may dissolve into the seawater from the hot water. Eventually, these are oxidized by the oxygen contained in the seawater, become oxides, and precipitate on the seabed, forming spherical (potato-like) manganese nodules. Manganese and iron oxides surround a core of shark teeth or rock fragments, forming a concentric structure.
These nodules, mainly composed of manganese and iron, also contain useful resources such as nickel, cobalt, and copper, and are known to exist in large quantities on the seabed worldwide, making them an important marine resource.

Manganese nodule collected from the Pacific Ocean seabed