Vesle Arøya, Langesundfiord, Southern Norway

© Tom Engvoldsen
Grenmarite
(Zr,Mn)2(Zr,Ti)(Mn,Na)(Na,Ca)4[Si2O7](O,F)4
Strunz VIII/C.11-10
Color yellowish brown, rose brown, red brown, dark brown
Luster vitreous - dull
Diaphaneity transparent to translucent
Streak very pale yellowish brown
Hardness 4½
Density 3.49, 3.568 g/cm3
Fracture brittle. uneven
Cleavage {001} good
Habit as semi parallel aggregates of elongated, flattened and often curved crystals up to 1 cm in length. Altered crystals are dark brown colored.
IMA status approved IMA 2004. Discovered 1989
Name Named after Grenmar - the Norse name of Langesundfiord
Locality TL Vesle Arøya, Langesundfiord, Southern Norway
Occurence
Crystallographical Data
System Monoclinic - Prismatic
Class 2/m
Group P 2/c
Z 2
Lattice a=5.608 b= 7.139 c=18.575 
β=102.60° 
Ratio a:b:c = 0.786 : 1 : 2.602
Optical Data
Type Biaxial (+)
RI nα=1.694
nβ=1.7135
nγ=1.735
2V 42°

Crystal Drawings
Mineral Pictures