For geologists, ice is a mineral, and a glacier is technically a rock.
Why it is true
A mineral is a natural, inorganic solid with a crystal structure and a defined chemical composition, and ice meets every condition. A rock is an aggregate of minerals, so a glacier, made of ice crystals, is a rock that happens to melt at 0 °C.
Source: International Mineralogical Association
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.
