Dear Colleague,

you can find in sandstones U in yellow ore, e.g., uranyl phosphates, silicates, in black ore minerals such as coffinite and pitchblende, in heavy minerals of different vulnerability grades from apatite (soluble in monochloro acetic acid) to zircon (hydrofluoric acid). The latter minerals need firstly a heavy mineral separation to make it fit for further chemical treatment.

There is succession of decreasing solubilities:

1. HF, 2. HCl very resistant 3. HCl higly vulnerable, 4. KOH, 5. H2O. All U minerals should have been cracked.

You can use dithionite soliution for U in Fe oxide hydrates.

A procedure for different types of silica has been proposed below.

DILL, H.G., STUMMEYER, J. and SIEWERS, U. (2002) Selective leaching of biogenic and geogenic silica in diatomaceous siliciclastics of the Kathmandu paleolake, Nepal.- Neues Jahrbuch für Mineralogie Mh., 2002 (1): 515-528.

This is also applicableto poorly crystallized U oxides.

It is important to know where the U is located , e.g. cement or detritus and whether there are clusters or disseminations by audioradiographic methods. Moreover XRD and (ore)microscopy need to be used prior to any differential leaching to get an overview of the lithological and mineralogical composition of the host.

There are no textbook-like or cookbook-like manuals. You must take some trial- and-error approaches.

This is to give you an overview from my experience as I have been with the U branch.

Good luck!

HGD