Bangladesh comprises geologically, for the most part, alluvial deposits, the results of tens of thousands of years snow melt water from the Himalayas, and seasonal cyclone flooding.
The result is astonishingly fertile agricultural land, as in most river delta lands across the globe. But these deposits cover underlying rocks which makes the availability of rock at stone, even for most basic construction purposes, difficult and expensive to access.
Underlying mineral resources includes coal and vast natural gas deposits, but gravel for concrete and building stone are hard won.
Each spring, the snows of the Himalayas continue to melt, and the waters of the many rivers that originate in the mountains carry rocks and stones across the border into stone starved Bangladesh.
There is an industry of fishing and diving for these huge quantities of precious rocks at most places on the border with India where the rivers cross.
At Point Zero, near Jaflong, on the north eastern border, this industry is particularly flourishing, and, together with the invaluable sans that is also part of this inflow, represents a major employer and commercial activity.
The river scenery of these northern streams makes a breathtaking backdrop to the strenuous and sometimes dangerous work. Yet another unique and fascinating attraction of this remarkable country.