| mineral |
hollandite structure |
description |
formula |
| ramsdellite |
 | black crystals which form on goethite spikes in geodes |
MnO2 |
| romanechite |
 | black spikelets |
(Ba,H2O)2Mn5O10 |
| hollandite |
 | black "matte" which forms in geodes |
MnO2 |
| todorokite |
 ,
 ,
 ,
 | black "beard" which forms on goethite |
(Mn,Ca,Mg)Mn3O H2O |
| burnessite |
layered |
desert varnish |
Structure not known |
| nsutite |
 ,
| |
[Mn(O,OH) H2O] |
| pyrolusite |
| |
|
