Substrate?

Hi everyone,

I came to an area in my country where I notice rock made up of small black gravels. The area covered with red soil, laterite, this particular rock and thick deposit of small grain of gravel (not mixing with laterite), possibly come off from the rock. Does anyone know what it is? Can I use it as substrate?

It is a village with plantations - low population density. The earth underneath, within 1 meter deep, covered with such kind of rock. Some in the pic above are magnetic kind of gravels.

Lol, my thought was that you were asking me if there's any valcano there and the area is population free. I would clean and try it out.