I think any sand from a fresh-water stream will be silica or silicate. The aragonite is from seashells crushed by tides. -----Original Message----- From: pbs [mailto:pbs-bounces@lists.ibiblio.org] On Behalf Of penstemon Sent: Saturday, November 15, 2014 5:08 PM To: Pacific Bulb Society Subject: Re: [pbs] Sand for potting mixes >I have heard for years that one needs to use “silica sand” for bulb >potting mixes. I wonder how “silica sand” differs from other sand. I >try to find very coarse sand because it is not as likely to compact. >The best stuff I found was from a stream bed. But was it “silica sand?” >Isn’t sand generally a silicate mineral anyway? I would have said yes, but a quick check of the apparently-omniscient Wikipedia says that silica sand is the most common form of sand, followed by sand from calcium carbonate (aragonite). The sand I use is the stuff called "paving sand"; comes in bags. The grains aren't uniform in size. Bob _______________________________________________ pbs mailing list pbs@lists.ibiblio.org http://pacificbulbsociety.org/list.php http://pacificbulbsociety.org/pbswiki/