The Brains Trust - 2020, page-1838

Do you mean mass per unit volume ?

There is a fair density variation between sandstone/ silt / clay and the relative abundance of these in a specific sedimentary sequence.

Also ore zones may differ to the broader sequence.

2.5 tonnes/ cubic metre would be fine. In my experience its just a guess but that is a fair number if you look at larger data sets.

I think you are better to watch the stock not the rock density thanks for bringing that one to my attention.