What is the Mohs hardness rating for iron?

The Mohs hardness scale is used to categorize minerals based on their ability to scratch one another, with talc rated at 1 (the softest) and diamond at 10 (the hardest). Iron, typically found in the form of various minerals such as hematite or magnetite, has a Mohs hardness rating of approximately 4.5 to 5.

The option indicating a hardness rating of 5 is correct because it aligns with the typical value attributed to metallic iron. This rating suggests that iron can scratch minerals rated lower than 5, such as gypsum (rating of 2) and calcite (rating of 3), while being scratched by harder materials like apatite (rating of 5) or quartz (rating of 7).

Other choices fall outside the typical hardness range for iron. A rating of 7 indicates minerals like quartz, which are harder than metallic iron, while 6 would suggest a hardness level that is not accurate for iron in its common forms. A rating of 3 would classify iron as significantly softer than it actually is in terms of its mineralogical characteristics. Thus, considering these factors, the correct Mohs hardness rating for iron firmly establishes it around the 5 mark.