Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Habit:
Massive - Granular - Common texture observed in granite and other igneous rock.
Habit:
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Hardness:
4-5 - Fluorite-Apatite
Luster:
Vitreous - Greasy
Streak:
white
Optical Properties of Bastnasite-(La)
Gladstone-Dale:
CI meas= 0.02 (Excellent) - where the CI = (1-KPDmeas/KC) CI calc= 0.038 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1514,KPDmeas= 0.1543,KC= 0.1574 Ncalc = 1.78 - 1.8
Optical Data:
Uniaxial (+), w=1.717, e=1.818, bire=0.1010.
Calculated Properties of Bastnasite-(La)
Electron Density:
Bulk Density (Electron Density)=4.38 gm/cc note: Specific Gravity of Bastnasite-(La) =4.98 gm/cc.
Fermion Index:
Fermion Index = 0.0012857193 Boson Index = 0.9987142807
Photoelectric:
PEBastnasite-(La) = 311.14 barns/electron U=PEBastnasite-(La) x relectron=1,363.84 barns/cc.
Radioactivity:
GRapi = 59,907.71 (Gamma Ray American Petroleum Institute Units)
Concentration of Bastnasite-(La) per GRapi unit = 16.69 (PPM)
Bastnasite-(La) is Radioactive as defined in 49 CFR 173.403. Greater than 70 Bq / gram.
Estimated Radioactivity from Bastnasite-(La) - weak
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 / 7.27 cm
1,427,855
3.86E-05
59,907.71
19.70
100 gm / 3.37 cm
142,786
3.86E-06
5,990.77
1.97
10 gm / 1.57 cm
14,279
3.86E-07
599.08
0.20
1 gm / 7.27 mm
1,428
3.86E-08
59.91
0.02
0.1 gm / 3.37 mm
143
3.86E-09
5.99
0.00
0.01 gm / 1.57 mm
14
3.86E-10
0.60
0.00
0.001 gm / 0.73 mm
1
3.86E-11
0.06
0.00
Weight of pure Bastnasite-(La) in grams (gm) and Calculated Diameter of a Sphere with a Density of 4.98 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 ( 3.19 % Th) From Sum REE Elements (63.74 % REE)
Chemical Formula: 
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- weak