The 5 most common forms of iron ore are (1) Magnetite (2) Hematite (3) Goethite (4) Limonite (5) Siderite. 

Mostly, iron ore is found in the form of oxides. But it is also present in the form of carbonate and sulfide.

What is Iron Ore?

Iron ore is a mineral found in nature from which ferrous metal can reasonably be extracted. Iron ore is actually rich in ferrous metal. Such as magnetite, hematite, goethite, and limonite are iron oxides while siderite is iron carbonate. Iron pyrite is also a mineral of iron sulfide.

How is Iron Ore formed?

Over billions of years ago, the oceans contained an abundance of iron but no dissolved oxygen(free oxygen in water). The iron ore started to deposit when the organisms became capable of photosynthesis and began releasing oxygen into the water. As free oxygen is available in water, dissolved iron begins to form hematite and magnetite.

Read The Effect of Tungsten on Steel and Different material.