Respuesta :

i believe it is Sand. because when sand hardens it's like a type of case that conceals things like bones hope this helps and have a great day :-) 
peterdaly
I would say that the burial material that would best preserve the fossils is silica since it is very hard ie quartz is the main consituent of silica has a hardness of 7 on the Mohs hardness scale of 1-10. Silica is resistant to weathering and erosion.