Due to transportation costs, pumice tends to be mined closest to where it is sold. It is unavailable in many parts of the US without special ordering, and I doubt sedimentary Europe has many sources. Different colors and particle sizes have been available. The mine in Arizona closed, and I have heard the same about the one on the slopes of Mount Shasta in California. Succulent growers in places where pumice is unavailable use the horse stall material, but wash it well with water and a screen to remove the fines. I use my pumice fines in some of my clay-like mixes. A lot of people make sure their pumice and perlite is wet before working with it to try and avoid breathing the dust. I use large-particle perlite for my succulents when I cannot get large-particle pumice. I will cover the mixture with a thick layer of sand or desert clay soil to prevent pumice from surfacing. I don't have the problem of pots staying wet too long in my climate. Leo Martin Zone 9? Phoenix Arizona USA