Silica sand comes in a number of grades from sugar-like (#30) to chicken grit-like (#12). It is usually used for sandblasting and is regulated by OSHA as a hazardous material because of the fine dust that can cause silicosis in the lungs. I believe the signal word is WARNING. (Perlite, by contrast, has what is officially regarded as a nuisance dust). Any silica sand user must abate the risk with rated respirators and follow all precautions given before use. Years ago, when I saw a very good collection of species Hippeastrum growing in mostly silica sand and coarse black lava rock, I decided to try it for bulbs more sensitive to rotting. My impression after a few years was that it did yield better results than the general purpose river sand that is commonly sold for concrete work. Silica sand is almost entirely free of silt and clay and the sharply angular grains seem to be favored by bulb roots that attach to them. I would mix this sand, usually #20, with pumice and less than 15% organic matter. I still like its performance very much but eventually the health risk outweighed horticultural benefits. Subsequently I did a little looking into what types of silica sand there are, looking for an angle because resuming the use of river sand was somewhat disappointing. From recollection, there are about a dozen recognized types of crystalline silica sand and a few types of amorphous (non-crystalline) silica sand. It is the former that poses the danger, while amorphous sand is not a health risk. This is due to the microscopic structure of the particles (invisible to the naked eye) that are sharp and abrasive in the crystalline types of silica sand. Translating this information into product sourcing is still a work in progress. Currently I am happy with a "play sand" that is similar to silica sand in appearance. It is nearly colorless and very clean, with a grade a little coarser than table salt. Dylan Hannon *"The greatest service which can be rendered any country is to add an useful plant to its culture..." --**Thomas Jefferson*