Name/Title
PsilomelaneEntry/Object ID
2004.1.165Description
Chemical Composition: Ba(Mn2+)(Mn4+)8O16(OH)4
Crystal System: Monoclinic System
Description: Common Name: Psilomelane, or black hematite
Group Name: Manganese oxides
Chemistry: Ba(Mn2+)(Mn4+)8O16(OH)4 or as (Ba,H2O)2Mn5O10
Location: Morocco
Description: Many smooth, black projections from base matrix. Overall shape is halfway between a fossilized coral look and a stalagmite look.
PHYSICAL CHARACTERISTICS:
Psilomelane, also known as black hematite, is a group name for hard black manganese oxides such as hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. It is sometimes considered to be a hydrous manganese manganate, but of doubtful composition. The amount of manganese present corresponds to 70-80% of manganous oxide with 10-15% of available oxygen.
Psilomelane is amorphous and occurs as botryoidal and stalactitic masses with a smooth shining surface and submetallic lustre. The mineral is readily distinguished from other hydrous manganese oxides (manganite and wad) by its greater hardness 5 to 6; the specific gravity varies from 3.7 to 4.7. The streak is brownish black and the fracture smooth. Owing to its amorphous nature, the mineral often contains admixed impurities, such as iron hydroxides. It is soluble in hydrochloric acid with evolution of chlorine gas.
Fracture: conchoidal & uneven
Hardness: 6 Orthoclase
Luster: Metallic
Occurrence: Psilomelane is found at many localities; amongst those which have yielded typical botryoidal specimens may be mentioned the Restormel iron mine at Lostwithiel in Cornwall, Brendon Hills in Somerset, Hoy in Orkney, Sayn near Coblenz, and Crimora in Augusta county, Virginia. With pyrolusite, it is extensively mined in Vermont, Virginia, Arkansas, and Nova Scotia.
Specific Gravity: 3.7 - 4.7
Streak: brownish black
Variety: Psilomelane is a common and important ore of manganese, occurring under the same conditions and having the same commercial applications as pyrolusite. Crystal habit: Botryoidal, Mammillary, ReniformCollection
Suomynona Mineral CollectionAcquisition
Accession
2004.1Source or Donor
Suomynona Mineral CollectionAcquisition Method
DonationDimensions
Width
4 inDepth
3-3/16 inLength
8-11/16 inDimension Notes
Dimension taken at widest pointsLocation
Location
Container
RightDrawer
BottomShelf
Right, RightWall
NorthBuilding
Founders RoomCategory
PermanentMoved By
Ray BlohmDate
February 20, 2012Location
Shelf
RightCabinet
Case # 7Room
Mentzer HallBuilding
Crater Rock MuseumCategory
Permanent
