Play Create Explore: Baby Oil Sensory Bags = baby oil, food colouring, a little bit of water, glitter, objects to find (smooth). Put in ziplock bag and duct tape for leaks and little fingers who would like to open it.
Hunting down a gorgeous antique aquarium could take some time (try eBay, flea markets, and vintage shops), but any glass vessel with a flat side brings crisp clarity to gnarly organic items. Fill the vessel less than halfway (much of the beauty is in the negative space), and arrange the biggest pieces on top. Blow away dust occasionally with a hair dryer set on cool.