I used crushed aggregate (called paver base) under pavers. It contains a range of particle sizes from powder to larger grains. I think it compresses better to bed the pavers than sand. But you certainly could use this sand. I don't know what you mean by seal them though.
The volume is 5.99 cubic gallons.
I just bought four bags and used them in a sand blast tank to blast an automotive utility trailer. It does appear to have silica, as it states on the bag that it is SILICA SAND.
Typical sand color
Dear Valued Home Depot Customer, We have reached out to the manufacturer and their reply is, 50# #0 Mesh Sand is always available at Home Depot stores in N. CA.
Cemex Play Sand is ocean sand that is washed and sterilized by kiln drying. No, it is not dangerous.
Jen: Thank you for your inquiry with HomeDepot.com. Unfortunately, Cemex 50 lb. 30 Mesh Sand is currently out of stock and does not have an ETA. Please check back on this webpage for updates. We hope this information is helpful, we appreciate your business.