Gold Mining BC.com

Gold Claims For Sale in BC

From Clay to Boulders

These are semi-standard sizes for the pieces of rocks and minerals that make up stream deposits (what geologists call clasts)...

From Clay to Boulders by Grain Size...

Clay extremely fine-grained plate-like minerals
(which water molecules find sticky)
Silt up to 1/400 inch     0.064 mm
Sand up to 1/10 inch       2.5 mm
Pebble up to 1/4 inch         6.4 mm
(may be called sand or gravel)
Gravel up to 2.5 inches     64 mm
Cobble up to 10 inches      256 mm
(may be called a boulder)
Boulder more than 10 inches     256 mm

 

Clay, Sand and Black Sand

Where They Come From

The trivial way first... rocks tumbling in a stream break and get smaller.

Weathering is more interesting...

Much of the Earth's crust is granite-like rock - minerals solidified out of molten rock. Granite is made up of three major kinds of minerals...