The following table is adapted (a little) from a handout given in my Geomorphology class. No source was given on the handout. The table shows (suggests, really) that the hardness of glacial ice increases as its temperature decreases. I think the point that is trying tomake, though, is that even very, very cold ice (-78.5°C, which seems very unlikely for a glacier to get so cold, especially considering the heat generated, and the thin layer of luricating water resulting from the basal sliding that would be required for abrasion) isn’t hard enough to scratch rocks as hard as quartz,making the case for most of theabrasive work of glaciers being done by debris that has been picked up movement of the glacier.

 

Table 1 – Hardness of Glacial Ice in Comparison to Representative Minerals and Common Items
MOH’S NUMBER
REPRESENTATIVE MINERAL
COMMON ITEMS (INLCUDING DIFFERENT TEMPERATURES OF GLACIAL ICE) WITH SIMILAR HARDNESS
1
Talc
Glacial Ice at 0°C
2
Gypsum
3
Calcite
Fingernail
4
Flourite
Copper Penny, Glacial Ice at -40°C
5
Apatite
6
Orthoclase
Knife Blade, Glass Plate, File, Glacial Ice at -78.5°C
7
Quartz
8
Topaz
9
Croundum
10
Diamond