Perlite

The reason that you have Perlite in a potting shed is that it makes an excellent media for keeping soil from clumping (an important point in Bentonite Country aka: the Front Range)and it is used in most potting soils.
Many eons ago when I manufactured Hydroponic Gardens, we used Perlite as a growing media. It was light weight enough for home use and had wonderful water retention capabilities. The big drawback to Perlite and Hydroponics is that it floats, a bad feature when you are giving plants their nutrients from water only.
The books recommend that you keep the perlite in place with washed Pea Gravel. This is too heavy for most peoples living rooms, so we substituted Idealite. Idealite was made in much the same way as perlite, but it was from exploded Shale. The Idealite name came from the company that invented the process, Ideal Cement Company, who used Idealite as a low-weight concrete mix. It was Ideal (pun intended) for our purposes. It was light weight and it didn't float in water.
The big drawback to using Perlite in Hydroponics is that over time it will mold.
We got the Idealite from the now closed Ideal plant at Rocky Flats.
Just an aside to an otherwise Railroad Discussion.
Rick