General Information:
Chemical Formula:
Ca2Mg2Fe+++4(Al,Fe+++)4Si2O20
Composition:
(Molecular Weight = 893.97 gm)
Calcium 8.97 % Ca
Magnesium 5.44 % Mg
Aluminum 6.04 % Al
Iron 37.48 % Fe
Silicon 6.28 % Si
Oxygen 35.79 % O
Empirical Formula:
Ca2Mg2Fe3+6Al2Si2O20
Environment:
Occurs in a paralava (pyrometamorhic melt rock) formed from burning coal beds.
IMA Status:
Approved IMA
Locality:
Druham ranch, 25 km S of Gillette in the Powder River Basin, Wyoming. USA.
Name Origin:
Named for John A. Dorr (1922-1986), University of Michigan.
Physical Properties:
Cleavage:
[001] Distinct, [010] Distinct
Color:
brownish black, dark brown, or reddish brown.
Diaphaniety:
Subopaque
Habits:
Anhedral Grains - Granular minerals without the expression of crystal shapes, Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).,
Hardness:
5 - Apatite
Luster:
Sub Metallic
More details...