Rhombohedral Crystals - Occurs as well-formed crystals showing rhobohedral crystals.
Hardness:
5-6 - Between Apatite and Orthoclase
Luster:
Metallic - Dull
Streak:
dark gray
Optical Properties of Crichtonite
Optical Data:
NCalc= 2.52 - from Gladstone-Dale relationship (KC = 0.3323) where Ncalc=Dcalc*KC+1 NCalc= 2.48 - from Gladstone-Dale relationship (KC = 0.3323) where Ncalc=Dmeas*KC+1
Calculated Properties of Crichtonite
Electron Density:
Bulk Density (Electron Density)=4.30 gm/cc note: Specific Gravity of Crichtonite =4.56 gm/cc.
Fermion Index:
Fermion Index = 0.05 Boson Index = 0.95
Photoelectric:
PECrichtonite = 47.08 barns/electron U=PECrichtonite x relectron= 202.44 barns/cc.
Radioactivity:
GRapi = 2,371.56 (Gamma Ray American Petroleum Institute Units)
Concentration of Crichtonite per GRapi unit = 421.66 (PPM)
Estimated Radioactivity from Crichtonite - mild
Specimen Size Weight/Volume (Sphere) *
Calculated Activity Bequerols (Bq)
Calculated Activity Curies (Ci)
Estimated Activity GR(api)
Estimated Exposure (mRem**)/hr If Held in Hand For One Hour
1000 gm / 7.48 cm
52,812
1.43E-06
2,371.56
0.78
100 gm / 3.47 cm
5,281
1.43E-07
237.16
0.08
10 gm / 1.61 cm
528
1.43E-08
23.72
0.01
1 gm / 7.48 mm
53
1.43E-09
2.37
0.00
0.1 gm / 3.47 mm
5
1.43E-10
0.24
0.00
0.01 gm / 1.61 mm
1
1.43E-11
0.02
0.00
0.001 gm / 0.75 mm
0
1.43E-12
0.00
0.00
Weight of pure Crichtonite in grams (gm) and Calculated Diameter of a Sphere with a Density of 4.56 gm/cc.*
Goverment Estimate of Average Annual Exposure (
360 mRem)
** Note: 10 microsieverts/hr = 1 mRem/hr **
Max Permissable Adult Dose 50,000 mRem/yr (hands), 15,000 mRem/yr (eyes)
Lethal Dose LD(50) Exposure 400,000 to 500,000 mRem
Estimated Thorium Activity ( 0.12 % Th) From Sum REE Elements ( 2.36 % REE)
Crichtonite Classification
Dana Class:
08.05.01.03(08)Multiple Oxides with Nb, Ta, and Ti
Chemical Formula: 
- mild