Formula: K(Mn,Fe,Fe)2(Nb,Ta)(PO4)2O2(H2O,OH)2
Origin of name: For Richard Johnson and Frank Walkup, American mineral technicians
Crystal system: Orthorhombic
Crystal class: mm2
Twinning:
Unit cell:
Colour: Dark reddish brown
Diaphaneity:
Luster: Vitreous
Habit: Crystals bladed, elongated on b-axis
Hardness: 4
Specific gravity: 3.40
Cleavage: 2; {001} and {100} good
Tenacity:
Streak: Greenish yellow
Synonyms/varieties:
Comments:
| Back to Alphabetical list | Colour photos | Thin sections | SEM images | TEM images | vibrational spectra description | IR spectra | Raman spectra | N-IR spectra | F-IR spectra | IES spectra |