Right now in Hokkaido, lucky visitors are able to see an unusual feat of nature. Jewelry ice or ice so clear that it looks like a precious stone can be found alongside the Tokachi River of Hokkaido. Having lived in cold parts of the world abundant with lakes and rivers before and never having seen jewelry ice, I wondered how this ice could form naturally clear. Of the several reasons which could explain the formation of jewelry ice, there are two that stand out.
In nature, water contains some degree of impurities; soil, dissolved minerals, bubbles, pollution etc. These impurities are frozen in place when the temperature drops, making the ice that forms cloudy and opaque. This same reasoning is why the ice cubes in your freezer are semi-opaque; trapped water bubbles that didn’t have a chance to escape before they were frozen in place. One reason why jewelry ice is clear could be that the water froze slowly over time giving impurities time to settle out and bubbles to float to the surface.
Another reason explaining the clarity of jewelry ice could be that the water by which it was formed simply contains very few impurities to begin with. Without a lot of obstacles to refract light, the ice appears clearer than ice formed in an environment with impurities present. The rivers in Hokkaido are generally known to be clean so it is possible jewelry ice is made from very pure water (this gives a more thorough explanation).
Seeing jewelry ice is a special treat for those brave enough to visit Hokkaido in the winter. While jewelry ice isn’t the only natural wonder to see in Hokkaido, its unusual and rare formation should put it on your list of spots to see this winter!
For more information check out the Toyokoro Website.