I doubt they would file at patent on the purification since it is so simple and obvious and this is one of the reasons to refuse a patent. If you consider that a patent allows you to prevent anyone else from practising the art and the fact that the Albany deposit is so rare, it might not make sense to go to the trouble of patenting this process. The other method of protecting things such as this is just to keep all or parts of the process proprietary and that makes it doublly hard for anyone to replicate: 1) because you do not publish the information as you are required to do so in a patent and so it is dificult to even work around proprietary processes eg Coke and 2) It would be more likely that the process of producing products such as certain types of surface area etc, or graphene would make more sense to patent. Just my 2 cents worth for what its worth, but I have filed quite a few patents.