CHAPTER VIII 

 GROUND LIMESTONE 



Variation in Quality. Limestones vary 

 widely in purity. They were formed under 

 water, and clay and sand were laid down 

 with the lime in such quantity in some cases 

 that the resulting stone is not worth han- 

 dling for soil improvement. A stone that is 

 practically all carbonate of calcium, or a 

 combination of calcium and magnesium, is 

 wanted because it is these two elements that 

 give value to the material. If a poor stone 

 is used, too much waste matter must be 

 handled. Twenty-five per cent more 

 ground limestone of 80% purity must be 

 applied than would be required in the case 

 of an absolutely pure limestone. Any stone 

 above 90% pure in carbonate of lime and 

 magnesia is rated as good, but the best stone 

 runs from 96% to 99%. 



Limestones vary greatly in ability to re- 

 sist disintegration, and this variation is a 

 big factor in determining the agricultural 

 value of ground limestone that has not been 

 reduced to a fine powder. Particles of a 



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