In the outer silicate zone of alteration surrounding hydrated uranyl oxides incrusting primary uraninite; also filling fractures at some distance from primary uraninite.
IMA Status:
Valid Species (Pre-IMA) 1956
Locality:
In the USA, from the Delta mine, Emery Co., Utah; the New Method mine, near Amboy, San Bernardino Co., California. Link to MinDat.org Location Data.
Name Origin:
For Bertram Borden Boltwood (1870-1927), radiochemist of Yale University, New Haven, Connecticut, USA, who devised the U-Pb method of measuring geologic time.
Fluorescent, Short UV=dull green, Long UV=dull green.
Luster:
Vitreous - Pearly
Streak:
white
Optical Properties of Boltwoodite
Gladstone-Dale:
CI meas= -0.346 (Poor) - where the CI = (1-KPDmeas/KC) CI calc= -0.338 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1901,KPDmeas= 0.1912,KC= 0.1421 Ncalc = 1.51
Estimated Radioactivity from Boltwoodite - very strong
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 / 8.08 cm
99,264,658
2.68E-03
4,162,622.33
1,368.53
100 gm / 3.75 cm
9,926,466
2.68E-04
416,262.23
136.85
10 gm / 1.74 cm
992,647
2.68E-05
41,626.22
13.69
1 gm / 8.08 mm
99,265
2.68E-06
4,162.62
1.37
0.1 gm / 3.75 mm
9,926
2.68E-07
416.26
0.14
0.01 gm / 1.74 mm
993
2.68E-08
41.63
0.01
0.001 gm / 0.81 mm
99
2.68E-09
4.16
0.00
Weight of pure Boltwoodite in grams (gm) and Calculated Diameter of a Sphere with a Density of 3.62 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
Boltwoodite Classification
Dana Class:
53.03.01.05(53)Nesosilicate Insular SiO4 Groups and Other Anions of Complex Cations
Chemical Formula: 
- very strong