Considerations when determining ice quality have changed across the years. Here is what it said in a 1921 home economics textbook:
Ice is frozen water, and is just as pure as the water from which it was made. Ice from a pond should never be dissolved in drinking water or other beverages. Artificial ice is made by freezing water in tanks, the freezing temperature being secured by the evaporation of ammonia. This ice should be much purer than ice from ponds, lakes and rivers.
Elementary Home Economics (1921) by Mary Lockwood Matthews