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www.mineralgallery.co.za Minerals F-J |
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Goethite |
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Name
Goethite
Chemistry
FeO(OH) Hydrated Iron Oxide
Uses
This is an important ore of iron and is also used as a coloring pigment
Color
Yellow, brown, black and even reddish. It can be tarnished with iridescent colors
Hardness
5
Specific gravity
3.5-4.3
Streak
Brown to orange yellow.
Crystals
Mostly botryoidal in a massive form but can also be fibrous to stalactitic.
Accompanied by:
Calcite, limonite, manganese, iron, and many other secondary minerals.
Similar to:
Limonite and botryoidal hematite.
Goethite is a common type of mineral due to the abundance of iron ore, but it can form brightly colored iridescent specimens. It can occur with other minerals to form interesting appealing specimens.
Goethite is produced by the oxidation of iron-bearing minerals such as pyrite and magnetite.
It is of widespread occurrence, though at one time it was thought to be a rare mineral. In fact much of the ocherous brown ferric oxide described as limonite is composed in a large part of crystaline goethite. Limonite has a yellowish brown streak and a vitreous luster which, together with the lack of cleavage, serves to distinguish it from goethite.
Goethite occurs as a secondary mineral in the oxidation zone of veins containing iron bearing minerals. It replaces other minerals, and goethite psued omorphs after pyrite are common.
