Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit:
Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Habit:
Massive - Granular - Common texture observed in granite and other igneous rock.
Hardness:
6.5 - Pyrite
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Fayalite
Gladstone-Dale:
CI meas= 0.055 (Good) - where the CI = (1-KPDmeas/KC) CI calc= 0.11 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1726,KPDmeas= 0.1833,KC= 0.1939 Ncalc = 1.85 - 1.9
Optical Data:
Biaxial (-), a=1.731-1.824, b=1.76-1.864, g=1.773-1.875, bire=0.0420-0.0510, 2V(Calc)=54-66, 2V(Meas)=74-47. Dispersion weak, r > v.
Pleochroism (x):
greenish yellow, pale yellow, or pale amber.
Pleochroism (y):
orange yellow, orange yellow, or orange yellow.
Pleochroism (z):
greenish yellow, pale yellow, or pale amber.
Calculated Properties of Fayalite
Electron Density:
Bulk Density (Electron Density)=4.22 gm/cc note: Specific Gravity of Fayalite =4.39 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEFayalite = 17.09 barns/electron U=PEFayalite x rElectron Density= 72.16 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Fayalite is Not Radioactive
Fayalite Classification
Dana Class:
51.03.01.01(51)Nesosilicate Insular SiO4 Groups Only
(51.03)with all cations in octahedral [6] coordination
Chemical Formula: 
