Tropical rainforest soil its red because it rains verry much .
This is where the stream used to flow.Because of the long term constant wash of water,the soil became red ,similarly to the soil in the rainforest.
This is the famous( or infamous) iron pan.It is a layer with more iron and manganese in it than the rest of the red soil and its hard almost like concrete.
The red coloration its from the iron and it looks like rust because thats what it is.
But its not just rust.
Tiny bits of shiny black among the most reddish portions are manganese but not all black its manganese only the verry small jet black concentrated bits.
On top of the iron pan and throughout it there are bacteria specialised in iron.These bacterias make the iron available for plants and they are in the dark grey / black portions.
I think that the iron pan has all the qualities and minerals of the tropical soil concentrated in it .It has same minerals as the red soil but much more dense and can be ,,diluted,, with regular soil,manure ,etc.
I took somme home.