Growing medium
Gastil (Thu, 12 Jul 2012 12:05:27 PDT)

Having heard good things about pumice on this list, 
I went to our OSH and purchased a small bag of Black Gold brand pumice. 
It was about 10 times heavier than I expected pumice to be, but they assured me that was just because it was wet. 
At home, I noticed it had a lot of dust, which I did not think I wanted in my growing medium 
(not having read the note from Jane yet about the dust containing useful minerals). 
When I washed the pumice, I noticed it sank. I expected pumice to float. 
The pumice in Baja California floats and resembles styrofoam. 
I wrote to Black Gold and they replied

"The Black Gold Pumice that you bought comes from a source in central Oregon, 
the same source we have used for a long time. Chances are that you will get the 
same type of pumice in California, Oregon and Washington, if you buy Black Gold. 
This is a denser pumice, but should not affect the porosity you are seeking. 
The dust comes from the pumice rubbing against itself in the packaging as it is moved around."

I also noticed when I washed it that I could sieve out the sizes to get pebbles for topping and 
grit to sand size for growing medium and could wash away the silt-sized sediment. 

- Gastil