Weathering of Granite

 The Weathering of Granite
The three photographs below show a coarse grained Granite with pink Orthoclase feldspar from the same locality. These specimens represent the weathering of granite.
 
1) The sample on the left is one that is almost pristine, with little weathering. Notice the pink Orthoclase, black Amphibole, and clear glassy Quartz. All these are hard, durable minerals.
 
 
2) This second photograph shows a piece of rock from the same Granite formation, but it has begun to weather; notice how the luster of the Orthoclase has become dull, and the color has begun to fade.
 
 
 
 
 
 
 
3) In this third photo (left) the Granite has crumbled into a pile of decomposing igneous minerals and their weathering products such as Clay, and other new sedimentary minerals. Such weathered material is called grus, and is commonly found at the base of Granite slopes. It is entrained and transported by rain, streams, and rivers to the sea to be deposited as sedimentary rock
 
 
Although it is not visible here the grus also has a fair amount of Clay mixed in with it, the sedimentary weathering produce of the Orthoclase
 

Contributed by Lynn Fichter 

 
 
Friday, October 10, 2014
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