Hausmannite

{{Short description|Mixed oxide mineral of manganese II and III: Mn3O4}}

{{Infobox mineral

| name = Hausmannite

| category = Oxide mineral

| image = Hausmannite-215565.jpg

| imagesize = 260px

| caption =

| formula = {{chem2|Mn^{II}Mn^{III}2O4}},
{{chem2|MnO*Mn2O3}}, or
{{chem2|Mn3O4}}

| IMAsymbol = Hsm{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight = 228.81 g/mol

| strunz = 4.BB.10

| system = Tetragonal

| class = Ditetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)

| symmetry = I4₁/amd

| unit cell = a = 5.76 Å
c = 9.46 Å; Z = 4

| color = Brownish black, grayish.

| habit = Massive – granular – common texture observed in granite and other igneous rock. pseudo octahedral – crystals show an octahedral outline.

| twinning = Repeated twins on {112}

| cleavage = [001] Perfect

| fracture = Uneven – flat surfaces (not cleavage) fractured in an uneven pattern.

| tenacity = Brittle

| mohs = 5.5

| luster = Submetallic

| refractive = n_ε = 2.15, n_ω = 2.46

| opticalprop = Uniaxial (−)

| birefringence = δ = 0.31

| pleochroism =

| streak = Dark reddish brown

| gravity = 4.7 – 4.84, average = 4.76

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity = Opaque, transparent on thin edges

| other = Anisotropism: Distinct, bireflectance: weak; O = light gray; E = dark gray.

| references = {{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Hausmannite |url=https://www.handbookofmineralogy.org/pdfs/hausmannite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=2 July 2022 |date=2005}}{{mindat|id=1832|title=Hausmannite|access-date=2 July 2022}}{{Cite web|last1=Barthelmy|first1=David|year=2014|url=https://www.webmineral.com/data/Hausmannite.shtml|access-date=2 July 2022|title = Hausmannite Mineral Data|website=Webmineral.com}}

}}

Hausmannite is a complex oxide, or a mixed oxide, of manganese containing both di- and tri-valent manganese. Its chemical formula can be represented as {{chem2|Mn^{II}Mn^{III}2O4}}, or more simply noted as {{chem2|MnO*Mn2O3}}, or {{chem2|Mn3O4}}, as commonly done for magnetite ({{chem2|Fe3O4}}), the corresponding iron oxide. It belongs to the spinel group and forms tetragonal crystals. Hausmannite is a brown to black metallic mineral with Mohs hardness of 5.5 and a specific gravity of 4.8.

The type locality is Oehrenstock (Öhrenstock), Ilmenau, Thuringian Forest, Thuringia, Germany, where it was first described in 1813. Locations include Batesville, Arkansas, US; Ilfeld, Germany; Langban, Sweden; and the Ural Mountains, Russia. High quality samples have been found in South Africa and Namibia where it is associated with other manganese oxides, pyrolusite and psilomelane and the iron-manganese mineral bixbyite. Wilhelm Haidinger (1827) named it in honour of Johann Friedrich Ludwig Hausmann (1782–1859), Professor of Mineralogy, University of Göttingen, Germany.