There is indeed a belt of alluvial tin ore ranging from Burma down to Indonesia.

FORBES: After Conflict Minerals Comes The Death Metal: Tin. And It's Apple's Fault Again.

De Beers is active in every category of industrial diamond mining: open-pit, underground, large-scale alluvial, coastal and deep sea.

FORBES: Anglo American Receives Final Regulatory Approval for De Beers Acquisition

Some of the little mountain streams would have eroded and then collected deposits of that cassiterite: alluvial deposits again.

FORBES: After Conflict Minerals Comes The Death Metal: Tin. And It's Apple's Fault Again.

Next year should be bountiful: alluvial soil is rich in nitrates and phosphates.

ECONOMIST: Lining up for a new life

Mui Ca Mau , Viet Nam, on the southern tip of the country, demonstrates ecological succession systems on new alluvial lands.

UNESCO: MEDIA SERVICES

There was an alluvial fan at the base of the mountain, for instance, that had some of the same sediments as Eberswalde.

NEWYORKER: The Martian Chroniclers

It includes peat bogs and raised bogs, alluvial and riverine forests, as well as complete cave systems, such as the Schrattenfluh and the Napf area.

UNESCO: Natural Sciences

The fertile alluvial plains that stretched almost endlessly outside the windows during the first half of the journey give way to an undulating red earth dotted with small rocky hills, scrub bushes and slender trees.

CNN: Center Cut

And there is a risk that the process might temporarily raise prices of conflict diamonds if big mining houses, finding their huge deep mines uneconomic, were to close them down for that would mean a better price for rebels, scratching around river beds for alluvial diamonds.

ECONOMIST: How to stop diamonds paying for nasty African wars