Limonite
Transmitted Off Cross Polarized Light Illumination

Limonite is FeO-OH-nH2O. It varies in color from very pale yellow to orange-brown, depending
on the amount of water in the matrix. The flakes often contain darker, less hydrated nuclei.
The form of the limonite particle reflects the shape of the interface between the oil and the
water layer. These flat sheets indicate a very flat, smooth interface. Limonite is amorphous
or cryptocrystalline but as it looses more water the nuclei convert to a more evident crystal
structure. There are at least five forms of FeO-OH that have distinctive crystal structures.
They include lepidocrocite, goethite, and others.