Limonite is an iron oxide hydroxide, often with variable amounts of water. It's a secondary mineral, meaning it forms from the weathering and alteration of other iron-rich minerals like pyrite or magnetite.
Here's how it works:
* Weathering: Iron-rich minerals are exposed to air and water.
* Oxidation: Iron in the minerals reacts with oxygen to form iron oxides.
* Hydration: Water molecules become incorporated into the structure, creating limonite.
Since limonite is a mineral, it can be found in various rocks, often as an aggregate, meaning many limonite crystals are clumped together.
Here are some common rocks containing limonite:
* Goethite: This is a crystalline form of limonite, often found in bog iron ore.
* Ironstone: This is a sedimentary rock containing high amounts of iron oxides, including limonite.
* Laterite: This is a soil type rich in iron and aluminum oxides, often containing limonite.
It's important to note that limonite is not a pure mineral, and its composition can vary. This means its color can range from yellow to brown to reddish-brown, and its hardness and density can also fluctuate.
