Ninemile Granite

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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"Rotten granite" is the name popularly applied in Wisconsin to crumbly red granite quarried south of Rib Mountain. Although often described as "weathered" it actually shows little sign of chemical alteration, so precisely how it came to be so crumbly is a mystery.

Typical appearance of "rotten granite" in the pits south of Rib Mountain.

This photo tells the story. A spheroidally weathered, exfoliating core surrounded by exfoliation lamellae and crumbled granite.
Granite core surrounded by crumbled granite.
A crumbled granite core, only slightly less crumbled than its surroundings.
An intact granite boulder.
Left: a large xenolith in a granite boulder.
Below: the large boulders were probably dumped here during excavation.

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Created 11 April 2007, Last Update 18 April 2007

Not an official UW Green Bay site

	Typical appearance of "rotten granite" in the pits south of Rib Mountain.



	This photo tells the story. A spheroidally weathered, exfoliating core surrounded by exfoliation lamellae and crumbled granite.
	Granite core surrounded by crumbled granite.
	A crumbled granite core, only slightly less crumbled than its surroundings.
	An intact granite boulder.
	Left: a large xenolith in a granite boulder. Below: the large boulders were probably dumped here during excavation.