So, I suspect that calcium carbonate sand might change the pH, and that is why it is undesirable for potting mixes? Dell Sent from Windows Mail From: penstemon Sent: Saturday, November 15, 2014 5:07 PM To: Pacific Bulb Society >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/