limonite

Brown hematite, or limonite, has a chestnut brown color and contains very nearly sixty per cent.

On weathering, magnetite commonly passes into limonite, the ferrous oxide having probably been removed by carbonated waters.

The green sand when weathered is brown or rusty coloured, the glauconite being oxidized to limonite.

When hematite rusts, the brownish-yellow or yellow iron oxide, limonite, results.