Goethite is a common iron mineral. It often forms by weathering of other iron-rich minerals, thus is a common component of soils. It may form excellent pseudomorphs after the original minerals particularly pyrite or marcasite. 
Goethite may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits. When present in sufficient quantities, it constitutes an important iron ore mineral. Only a few of the most important goethite localities in the state will be mentioned here.
What's on the rock
Plattnerite
Formula:  
PbO2
Strunz: 
4.DB.05
Crystal System: 
Tetragonal
Hardness: 
5.5
Type Locality: 
 
Leadhills, South Lanarkshire, Strathclyde (Lanarkshire), Scotland, UK
Goethite
Formula: 
 
α-Fe3+O(OH)
Strunz: 
 
4.00.
Crystal System: 
 
Orthorhombic
Hardness: 
 
5.0 - 5.5
Type Locality: 
 
Hollertszug Mine (Hollerter Zug Mine), Dermbach, Herdorf, Siegerland, Rhineland-Palatinate, Germany
Hemimorphite
Formula: 
 
Zn4Si2O7(OH)2·H2O
Strunz: 
 
9.BD.10
Hardness: 
 
4.5 - 5.0
Streak:  
White
Type Locality: 
Băiţa Mining District (Baita Bihor; Rézbánya), Nucet, Bihor Co., Romania