Environment: Replacing uraninite, as a late-stage hydrothermal alteration product.
Locality: Spruce Pine district, from the Deer Park and other mines, Mitchell County, North Carolina, USA. Link to MinDat.org Location Data.
Name Origin: Named for Frank Wigglesworth Clarke (1847-1931), prominent American geochemist of the US Geological Survey.
Location: Bjertnes,Krøderen, Buskerud, Norway. Scale: Picture size 8 mm.
Color: Brown, Brownish yellow, Dark brown, Reddish brown.
Optical Data: Biaxial (-), a=1.997, b=2.098, g=2.108, bire=0.1110, 2V(Calc)=32, 2V(Meas)=30-50. Dispersion relatively weak.
Pleochroism (y): less dark orange.
Pleochroism (z): more dark orange.
note: Specific Gravity of Clarkeite =6.61 gm/cc.
Clarkeite is Radioactive as defined in 49 CFR 173.403. Greater than 70 Bq / gram.
Estimated Maximum U.S. Postal Shipping Size (10 mRem/hr limit, Unshielded 10 cm box) 6.35 ± 1.59 grams of pure Clarkeite .
Estimated Maximum U.S. Postal Shipping Size (10 mRem/hr limit, Unshielded 100 cm box) 635.31 ±158.83 grams of pure Clarkeite .