Pyrophanite

Pyrophanite is a manganese titanium oxide mineral with formula: MnTiO3. It is a member of the ilmenite group. It is a deep red to greenish black mineral which crystallizes in the trigonal system.

Pyrophanite
General
CategoryOxide mineral
Formula
(repeating unit)
MnTiO3
Strunz classification4.CB.05
Dana classification4.3.5.3
Crystal systemTrigonal
Crystal classRhombohedral (3)
(same H-M symbol)
Space groupR3
Unit cella = 5.13948(7) Å,
c = 14.2829(4) Å; Z = 6
Identification
ColorDeep blood-red to greenish black
Crystal habitRarely as rosettes of hexagonal plates, typically granular, scaly; occurs as exsolution lamenae in franklinite and spinel
CleavagePerfect on {0221}
FractureConchoidal
TenacityBrittle
Mohs scale hardness5–6
LusterSubmetallic
StreakOchre yellow
DiaphaneitySubtranslucent to opaque
Specific gravity4.537 measured
Optical propertiesUniaxial (-)
Refractive indexnω = 2.481 nε = 2.210
Birefringenceδ = 0.271
Common impuritiesFe, Zn
References[1][2][3]

Discovery and occurrence

It was first described in 1890 from an occurrence in the Harstigen Mine, Filipstad, Värmland, Sweden.[2] Its name was derived from the Greek πΰρ, fire, and φαίνεσθαι, to appear, because of the deep red color of the mineral.[2]

Its main occurrence is in manganese deposits that have undegone metamorphism. It also occurs in granite, amphibolite and serpentinite as an uncommon accessory mineral. Associated minerals include ilmenite, geikielite, hematite, spinel, gahnite, chromite, magnetite, ganophyllite, manganophyllite, hendricksite, garnet and calcite.[1]

References

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