(Science: chemical) hydrous sesquixoide of iron, an important ore of iron, occurring in stalactitic, mammillary, or earthy forms, of a dark brown colour, yellowish brown powder. It includes bog iron. Also called brown hematite.
Results from our forum
... gel which is deposited at relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, and basalt. Opal is one of the mineraloids that can form or replace fossils. The resulting fossils, though not of any ...
See entire post