Gravel is a semi-processed material which is used in the production of Concrete Slabs, Filter Media, and Sand. Gravel is produced solely by processing Rock in a Crusher and cannot be directly mined naturally.
Prior to Beta 0.3.11 (2022-01-23), the only method of obtaining Sand was directly mining it on the island, with no external sources such as outposts or trading. Thus, Sand was often the limiting factor in how much Glass a colony could produce and ultimately a limiting factor for progression. With this patch, the recipe to create Sand from Gravel by processing it in a Crusher was added. This change greatly increased the amount of Sand which is available on a given island.