Reddish-brown dorrite crystals from Chelyabinsk, Russia
General
Category
Inosilicate Sapphirine supergroup
Formula (repeating unit)
Ca2Mg2Fe43+(Al4Si2)O22
IMA symbol
Dor[1]
Strunz classification
9.DH.40
Dana classification
69.2.1a.2
Crystal system
Triclinic Unknown space group
Unit cell
a = 9.98, b = 5.08 c = 5.24 [Å]; β = 99.9°
Identification
Formula mass
893.97 g/mol
Color
Dark red-brown to dark brown
Crystal habit
Anhedral; Small prismatic crystals; Pseudomonoclinic
Twinning
Common, producing a pseudomonoclinic symmetry
Cleavage
Good cleavage assumed to be parallel to {010} and {001}
Fracture
Irregular
Mohs scale hardness
5
Luster
Submetallic
Streak
Grey
Diaphaneity
Subopaque
Density
3.959 g/cm3
Refractive index
α=1.82 β=1.84 γ=1.86
Birefringence
δ = 0.040
Pleochroism
X=red-orange to brown Y=yellowish brown Z=greenish brown
2V angle
90°
Absorption spectra
Very strong
References
[2][3]
Dorrite is a silicate mineral that is isostructural to the aenigmatite group.[2] It is most chemically similar to the mineral rhönite [Ca2Mg5Ti(Al2Si4)O20], made distinct by a lack of titanium (Ti) and the presence of Fe3+.[2] Dorrite is named for Dr. John (Jack) A. Dorr, a late professor at the University of Michigan that researched in outcrops where dorrite was found in 1982.[3] This mineral is sub-metallic resembling colors of brownish-black, dark brown, to reddish brown.
^ abcCosca, Michael A.; Rouse, Roland R.; Essene, Eric J. (December 1988). "Dorrite [Ca2 (Mg2 Fe3+4)(Al4Si2) O20], a new member of the aenigmatite group from a pyrometamorphic melt-rock". American Mineralogist. 73 (11–12): 1440–1448.
^ abBarthelmy, Dave. "Dorrite Mineral Data". webmineral.com. Retrieved 11 December 2015.
Dorrite is a silicate mineral that is isostructural to the aenigmatite group. It is most chemically similar to the mineral rhönite [Ca2Mg5Ti(Al2Si4)O20]...
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Esseneite Reddish-brown dorrite crystals associated to orange essenite, and also spinel and magnesioferrite. From: Chelyabinsk, Chelyabinsk Oblast, Russian...
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