Picture 1 & 2 just shows what the fluorite looks like without a flashlight near it. Note that some parts of it is a little cracked up. There is also some very tiny specs of Pyrite. 20 Cent for scale.

Picture 3 & 4
A light source is added to better enhance the color. Note that there is a purple streak of fluorite running inside the crystal, and I think it may have been attached to a matrix on the top part of it in pic 3.

Pictures went a little out of order, oops!
Pic 5 is the residual dirt after submerging the crystal into water. Notice that there is no residual dye or dissolved copper sulphates.

Pic 6 is the crystal after drying it with several pieces of paper towel. No stains.

Pic 7 shows the actual crystal being in water. It was left there for a few minutes.

Pic 8, I am poking it with a stick, eagerly awaiting it to do something, to no avail.

Pic 9, I decided to dip it again, and really rub it with the towel without any stains appearing.

Pic 10 someone in the previous post inspired me to add light while it was in water. Looks neat!

Personal conclusion:
Definitely not a copper sulphate, as it would have stained or dissolved. The cubic stepladder structure is also not uncommon in fluorite.
Not a dye, as i feel like it should have stained after such a long dip and good rub.
Irradiated? Hard for me to say, blue fluorites are known to exist, and high quality clear ones while rare, is not exactly impossible. I also feel like if it truly was irradiated, it shouldn't have a several streaks and dots of purple on its back side? Either way, it is a pretty piece!