If you Google Albert Einstein Hospital and then go to "images", there is a photo of the columns being erected in front of the hospital. The caption identifies the columns as the ones from the mint.

I was able to find one picture online. It's on the website of an engineering consulting firm, and it sounds like the columns were removed and placed in storage. That would explain why it is so difficult to find images of them online.

Prepared and developed construction documents for the removal and storage of six historic columns. Standing 30 feet and weighing 28,000 lbs, the columns were originally designed by William Strickland. The columns were part of the United States Mint in downtown Philadelphia and later donated to the hospital in 1904. These columns were originally constructed in the 1800's.

I found the pillars from the Philadelphia Mint! They are on the corner of Gerrit St and S 5th St in Phili, the building looks like it's closed. I'll send you a link from Google Earth. The reason the others couldn't find it was that they were looking at the new hospital, not the old one.

I'm not so sure these are the mint columns. There were six of them, not four, and the PBS Show said they were currently freestanding.

The other two columns are in the hospital's alleyway behind a fence just around the corner to the right of this image. I have a feeling other parts of the building were used as-well.

I would suggest asking one of your readers to go and personally inspect these columns to see if they are granite and if they have been plastered-over. It may also be a good idea to see if the building is going to be demolished.

The story about what happened to the Mint's columns was headlined the "third Philadelphia Mint", but the accompanying illustration pictured the second Philadelphia Mint. Of course, you could say that you were counting John Harper's cellar as the first one, and then everything would fit!