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» Online Classroom   »   » Public Discussion of Inland and Coastal Navigation   » Sizes of charted rock fragments

   
Author Topic: Sizes of charted rock fragments
David Burch


 - posted March 20, 2004 12:43 PM      Profile for David Burch           Edit/Delete Post 
Mud, Silt, clay:
— smaller than sand

Sand:
— very fine = 0.0625 to 0.125 mm
— fine = 0.125 to 0.25 mm
— medium = 0.25 to 0.5 mm
— coarse = 0.5 to 1 mm
— very coarse = 1 to 2 mm

Stones:
— gravel = 2 to 4 mm (BBs to small marbles)
— pebble = 4 to 64 mm (small marbles to tennis balls)
— cobble = 64 to 256 mm (tennis balls to soccer balls)
— boulder = bigger than cobbles, generally rounded

"Stones":
— aggreate of gravel, pebbles, and cobbles

Shingle:
— mixture of large pebbles and cobbles, from 16 to 256 mm

For converstion to sizes of typical things:
25.4 mm = 1 inch

Details such as give above can be found in the NOAA Nautical Chart Users Manual. This is available at no charge as a pdf file from NOAA, or we offer a printed, coil-bound copy in the books section of our catalog.

See: Chart Manual online or Book catalog index.

From: Starpath, Seattle, WA


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