Dorrite
A variety of Minerals
What is Dorrite?
Dorrite is a silicate mineral that is isostructural to the aenigmatite group. Although it is most chemically similar to the mineral rhönite [Ca2Mg5Ti(Al2Si4)O20], the lack of titanium (Ti) and presence of Fe influenced dorrite's independence. 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. This mineral is sub-metallic resembling colors of brownish-black, dark brown, to reddish brown.
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Key Characteristics
Formation of Dorrite
Dorrite can be found in mineral reactions that relate dorrite + magnetite + clinopyroxene, rhönite + magnetite + olivine + clinopyroxene, and aenigmatite + pyroxene + olivine assemblages in nature. These assemblages favor low pressures and high temperatures. Dorrite is stable in strongly oxidizing, high-temperature, low-pressure environments. It occurs in paralava, pyrometamorphic melt rock, formed from the burning of coal beds.
Composition of Dorrite
Calcium 8.97%Magnesium 5.44%Aluminum 6.04%Iron 37.48%Silicon 6.28%Oxygen 35.79% Oxides CaO 12.55%MgO 9.02%Al2O3 11.41%Fe2O3 53.59%SiO2 13.44%
Quick Facts
Physical Properties
- Color
- red-brown, brown-black, dark brown
- Hardness (Mohs)
- 5.5
- Streak
- brownish grey
Chemical Properties
- Chemical Formula
- Ca4(Mg3Fe3+9)O4(Si3Al8Fe3+O36) Idealized formula for Kopeisk material: Ca4Mg4Fe3+8[Al8Si4O20]
- Elements
- Al, Ca, Fe, Mg, O, Si
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