Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Habit:
Massive - Granular - Common texture observed in granite and other igneous rock.
Habit:
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Hardness:
7 - Quartz
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Cordierite
Gladstone-Dale:
CI meas= -0.008 (Superior) - where the CI = (1-KPDmeas/KC) CI calc= -0.077 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2224,KPDmeas= 0.2081,KC= 0.2065 Ncalc = 1.51 - 1.57
Optical Data:
Biaxial (-), a=1.527-1.56, b=1.532-1.574, g=1.538-1.578, bire=0.0110-0.0180, 2V(Calc)=54-86, 2V(Meas)=75-89. Dispersion weak, r < v.
Pleochroism (x):
colorless, pale yellow, or pale yellow.
Pleochroism (y):
colorless, violet, or blue.
Calculated Properties of Cordierite
Electron Density:
Bulk Density (Electron Density)=2.63 gm/cc note: Specific Gravity of Cordierite =2.65 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PECordierite = 1.65 barns/electron U=PECordierite x rElectron Density= 4.32 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Cordierite is Not Radioactive
Chemical Formula: 
