drysdallite-a proxy for uranium?, page-4

One of the three important types of uranium occurance in Zambia has occured in Karoo sandstones; associated with the copper mineralization of the Copperbelt. The copperbelt has produced in excess of one billion tonnes of ore (c.2.7% Cu) and conservative estimates suggest that a further two billion tonnes await exploitation.

info from http://www.zambia-mining.com/economicright.html (don't know how accurate but as an overview, gives you something)

I think he's trying to say Drysdallite=Uranium=A big copper deposit. That's just taking a stab.