Ullmannite

Nickel-rich assemblages within Mississippi Valley-style mineralization(a,b,d)

Ulvöspinel

Extraterrestrial rocks and olivine nodule(e)

Carbonatites(d)

Uraniferous carbon

Fossil placer(c)

Uraninite

Uranium vein association(a-f)

Fossil placer(b,c)

Carbonate-hosted base-metal mineralization(e)