soil classification according to the Massachusetts institute of technology. it was developed by Prof.G. Gilboy.
	in this system soil is divided into four groups.
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		1. gravel particle, size greater than 2mm.
 
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		2. sand particle, size between 0.06 to 2mm
 
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		3. silt particle, size between 0.002 to 0.06mm
 
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		4. clay particle, size less than 0.002mm"