CYS EXCEL X-Large 1 Inch Light Blue Glass Marble Gemstone Vase Fillers, 1 LB

Are they almost perfectly round? Can I Use them in a marble sculpture track?

If the clear marbles are to be in direct contact with plant roots, would one need be concerned of the chances of unintended toxins entering the plant?

Are these clear glass and perfectly round? Thanks!

what size are these in terms of mm?