River sand

 is a crafting resource which is gathered from waterways, requiring any shovel. It is a necessary ingredient when making most glassware. You can access the sand mining after talking with the bishop about a special request.

Recipe
These requisite sand mounds are scattered throughout the world, always found near water. There are five locations in total, four of which are on each corner of the local waterfall, with the fifth located along the beach, north-east of the Village and north of the Lighthouse.