All solid materials can be measured for hardness on the Mohs scale. The scale was created in 1812 by Freidrich Mohs and is based how easily one substance can scratch another. Diamond is the hardest rated at a 10 while talc is a very soft 1.
Suprisingly, Corn Cob Grit and iron have the same hardness at about 4.5. Even more amazing is that Corn Cob Grit is harder than brass (3-4), copper (2.5-3) and aluminum (2-3).
The really cool thing is that blasting with Corn Cob Grit won’t frost or pit glass and can be used to absorb grease, oils and water from metal surfaces. Corn Cob Grit is also great for blasting on wood surfaces (more to come on that). I wouldn’t recommend using iron grit near glass or on wood!