Contents

Plate	Photo Description
1	(a) - (d) — Fully developed uranium halos in mica (biotite)
2	(a) - (d) — 210Po halos in mica (biotite); (a) — also with a 218Po halo
3	(a) - (d) — 214Po halos in mica (biotite)
4	(a) - (d) — 218Po halos in mica (biotite)
5	(a, b & d) — Elliptical (compressed) 210Po halos in coalified wood; (c) — Dual 210Po halo in coalified wood
6	Uranium halos in fluorite in different stages of development: (a) - (b) — Embryonic; (c) - (d) — Fully developed; (e) — Overexposed, first-stage reversal; (f) - (g) — Overexposed, second-stage reversal; (h) — Overexposed, third-stage reversal
7	(a) - (h) — 210Po halos in fluorite
8	(a) - (h) — 218Po halos in fluorite; (c) — center darkened by electron microbeam analysis
9	(a) — 218Po halos in mica (biotite); (b) — Spectacle halo in biotite; (c) - (d) — 214Po halos in biotite
10	(a) — Overlapping 210Po halos in biotite, using phase contrast; (b) and (d) — Thorium halo and giant halo in Madagascan mica; (c) — Dwarf halos in Ytterby mica; (e) - (f) — Assortment of different polonium halo types in biotite; (g) — 214Po halos in biotite; (h) — A 210Po and a 214Po halo in biotite
11	(a) — Biotite crystal from Murray Bay, Canada; (b) — Po halo containing specimens of granite from New Hampshire, the dark areas are biotite crystals; (c) — Zircon crystals extracted from granite drill cores taken from a depth of about 15,000 ft.; (d) — Rhyolite from 1,683.3 ft. (specimen obtained from J. Eichelberger, Sandia National Labs)

Approximate Magnification
	(a)	(b)	(c)	(d)	(e)	(f)	(g)	(h)
1	×900	×1015	×1120	×1015
2	×540	×875	×875	×770
3	×800	×800	×800	×865
4	×930	×730	×965	×985
5	×500	×500	×500	×500
6	×725	×725	×880	×725	×725	×725	×725	×725
7	×725	×725	×725	×860	×725	×725	×725	×725
8	×725	×725	×725	×725	×725	×725	×725	×725
9	×245	×575	×165	×265
10	×420	×250	×500	×250	×275	×140	×275	×260
11	*	*	×300	*

* Scale shown in figure