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
Category	Oxide mineral
Formula (repeating unit)	MnTiO3
Strunz classification	4.CB.05
Dana classification	4.3.5.3
Crystal system	Trigonal
Crystal class	Rhombohedral (3) (same H-M symbol)
Space group	R3
Unit cell	a = 5.13948(7) Å, c = 14.2829(4) Å; Z = 6
Identification
Color	Deep blood-red to greenish black
Crystal habit	Rarely as rosettes of hexagonal plates, typically granular, scaly; occurs as exsolution lamenae in franklinite and spinel
Cleavage	Perfect on {0221}
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	5–6
Luster	Submetallic
Streak	Ochre yellow
Diaphaneity	Subtranslucent to opaque
Specific gravity	4.537 measured
Optical properties	Uniaxial (-)
Refractive index	nω = 2.481 nε = 2.210
Birefringence	δ = 0.271
Common impurities	Fe, Zn
References	[1][2][3]

Discovery and occurrenceEdit

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. 

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.