I have never noticed Unique being that dirty. During one of the shortages when I was about out I did some experimenting with other powders. American Select, 20/28, and e3 come to mind. They worked fine for my target ammo needs. I have bought another #8 jug of Unique, but I am still loading American Select in most of my 38 Special and 45GAP range loads.
Then I worked up loads for the 45GAP, using about every non-magnum handgun and shotgun powder I could locate samples of. What I discovered was lots of different powders worked very well. The only one I was not reasonably impressed with was 800X.

With that out of the way. If I were to stock up for a very long dry spell Unique, WW748, and Red Dot would be the three powders that would load 90% of the ammunition that I shoot. Unique has been getting the job done very well for a very long time.

Bob R