J 35 
Working on the principles outlined above, an attempt might 
even be made to estimate the age of the mineral in years. The 
figures are : — 
U 3 0 3 in mineral 26.58 per cent. 
U 3 Og equal to Th 0 2 in mineral 6.26 per cent. 
Total U, 0 8 32.84 per cent. 
U in one gram of mineral 0.2785 gm. 
Ra per 1 gm. of U 3.4 x io - ? gm. 
Ra per 1 gm. of mineral 9.47 x 10 3 gm. 
He evolved per year per 1 gm. Ra. . . . 3.16 x 10 1 c.c. 
He evolved per year per 1 gm. mineral 29.9 x 10-9 c.c. 
He found in 1 gm. mineral 0.385 c - c - 
Age of mineral in years, o.385-;-(2g.9xc. 10-9 c.) - 13 millions. 
At least two counterbalancing effects vitiate the above result to 
an unknown amount. These are the leakage of helium from the 
mineral before its estimation and secondly the unknown amount 
fo helium generated by the parent mineral and retained by 
Pilbarite at the outset of its existence as such. 
It is evident from what has been said that Pilbarite is 
strongly radioactive. To test this photographically a special 
rapid plate was covered by a sheet of black glazed paper which 
was again covered by a mask of lead foil pierced by a pattern. 
Over the lead foil was a sheet of thin tissue paper and on that a 
heap of powdered Pilbarite was placed. After 48 hours the plate 
was developed and a strong radiograph obtained, of the per- 
forations in the lead. An appreciable amount of radiation ha.d 
also passed through the lead foil, which was only 0.13 mm. in 
thickness, the outlines of the heap of powdered mineral being 
clearly discernible. 
A freshly scraped fragment of Pilbarite placed in a Glews 
scintilloscope yields a rapid succession of flashes due to the 
emission of alpha rays, i.e., to the impact of electrically charged 
atoms of helium on the screen of zinc sulphide. 
Heated in a closed or open tube, Pilbarite gives off much 
water and darkens somewhat in color. Before the blowpipe on 
charcoal it is infusible and turns black. If some of the powdered 
mineral be heated with sodium carbonate on charcoal, a black 
slag is formed in which small globules of metallic lead can be seen. 
A fragment heated in a microcosrnic salt bead gives the reactions 
of uranium, an unaffected residue of silica and thorium remaining. 
A search was made for evidences of radioactivity in the 
hornblende schists enclosing the lode in which Pilbarite occurs. 
When a small crystal of even a moderately radioactive mineral 
(such as radium- bearing varieties of zircon, apatite or allanite) 
is enclosed in hornblende, biotite or other similar mineral, the 
