Small traces of iron are responsible for much of the color found in corundum (saphire) gems. Ruby, however, does not contain iron and will not be affected by a magnet. To be technical however, I should point out that corundum is not magnetic. Corundum will not attract other pieces of iron to itself (as far as I know). To simply answer that corundum is not magnetic would have been misleading.
The overwhelming use, by far, of corundum is in the manufacture of abrasives--sandpaper, grinding wheels, etc. Gem grade corundum is used in jewelry.
Corundum can scratch almost any mineral that isn't diamond.
Glassy
Corundum is the 2nd hardest natural mineral discovered. For more information click on the related link.
Small traces of iron are responsible for much of the color found in corundum (saphire) gems. Ruby, however, does not contain iron and will not be affected by a magnet. To be technical however, I should point out that corundum is not magnetic. Corundum will not attract other pieces of iron to itself (as far as I know). To simply answer that corundum is not magnetic would have been misleading.
Corundum.
Corundum ( (Al_2O_3) ) is hexagonal in crystal structure.
Corundum is used for jewlery
Red corundum is called ruby.
Corundum is aluminium oxide, Al2O3.
Pure corundum is clear in color.
Corundum is in the trigonal crystal system.
Diamond is the hardest mineral and is the only one that can scratch corundum. but in my opinion corundum will scratch corundum any mineral of the same hardness will scratch the other !
Red corundum is called ruby.
100% of rubies are corundum. "Ruby" is a name made up by the gem trade for the mineral known as corundum, when it is red.
Corundum is a mineral, therefore it could not be the hardest rock.