Formula: K(Fe,Mg,Fe)8(Si,Al)12(O,OH)27
Origin of name: from Greek for shining and black
Crystal system: triclinic
Crystal class: -1
Twinning:
Unit cell: a = 21.9 Å, b = 21.9 Å, c = 17.7 Å, a = 125°, b = 95.9°, g = 120°
Colour: black, deep reddish brown, golden brown, dark green
Diaphaneity: translucent
Luster: pearly to subvitreous
Habit: foliated plates, coatings, fibrous or velvety
Hardness: 3
Specific gravity: 2.59
Cleavage: 2; {001} perfect, {010} imperfect
Tenacity:
Streak:
Synonyms/varieties: chalcodite, ekmanite (Mn-rich variety), minguettite
Comments:
| Back to Alphabetical list | Colour photos | Optical properties/Thin sections | SEM images | TEM images | vibrational spectra description | IR spectra | Raman spectra | N-IR spectra | F-IR spectra | IES spectra |