It's important to clarify that "iron hardness" is a bit ambiguous. Iron itself is a metal, and metals don't have a single, universal "hardness" like a rock or a gemstone.

Here's what you need to know about the hardness of iron:

* Hardness Scale: We measure hardness using various scales, the most common being the Mohs Hardness Scale. This scale ranks minerals from 1 (softest - talc) to 10 (hardest - diamond). Iron, as a pure element, would be considered too soft to be measured on the Mohs scale.

* Iron's Mechanical Properties: Iron's hardness depends greatly on its alloying elements (what other elements are mixed in), processing (heat treatments, forging, etc.), and microstructure.

* Pure Iron: Relatively soft and ductile.

* Steels: Iron alloys with carbon and other elements. These can be extremely hard depending on the composition and processing. Some steels are harder than common minerals like quartz (Mohs hardness 7).

* Cast Iron: Iron alloys with carbon and silicon. Cast iron is generally harder than pure iron but less hard than some steels.

In summary:

* Pure iron is not hard enough to be measured on the Mohs Hardness Scale.

* Iron alloys (like steel and cast iron) have varying hardness levels, which are determined by their composition, processing, and microstructure.

If you're interested in the hardness of a specific iron alloy, you'll need to specify the type of iron and its properties.