It depends on your chosen location. For example, if you want to bury in a cemetery or an urn garden, these locations will have the final say on the appropriate type of urn. Usually, they will require an urn vault as well. For natural burial grounds, it is common to use urns made of natural materials that will decompose relatively quickly. For private lands, especially if it’s in your owned plot, you may be free to choose whichever urn or container you prefer, provided that you abide by local ordinances.