Originally Posted by beaslbob
There used to be a silica free tropical play sand that used to say right on the bag not fit for aquarium use.
Why the heck would a "silica" free sand make any difference to sand boxes and the like, I get why you wouldn't use silica free in a FW tank.
To clarify the OP's sand choices, the one posted is beach sand but it states lake sand in the information and silica quartz in the ingredients. Calling it beach sand makes it suitable for use in making sand castles and stuff... I think it even said that.
Individually those terms, lake sand and silica quartz, would assure me that the sand is suitable for the aquarium as lake sand is a quartz based sand and silica quartz (redundant term to be honest) is an inert material for any of our purposes.
At least our cleaning process doesn't get this involved, or at least we can stop after the first sentence:
Cleaning the quartz grains and increasing silica content is achieved by washing to remove clay minerals and scrubbing by attrition between particles. Production of the optimum size
distribution is achieved by screening to remove unwanted coarse particles and classification in an upward current of water to remove unwanted fine material. Quartz grains are often iron
stained and the staining may be removed or reduced by chemical reaction involving sulphuric acid at different temperatures. Impurities present as separate mineral particles may be removed by various processes
including gravity separation, froth flotation and magnetic separation. For the highest purity, for electronics applications, extra cleaning with aggressive acids such as hydrofluoric acid
combined with thermal shock may be necessary.