Lake Ellen Kimberlite the material, though few are of gem quality and size. While there was considerable interest in diamond exploration in Michigan’s Upper Peninsula and northern Wisconsin for several years, no diamonds of commercial interest have been found. Lake Ellen Kimberlite The Lake Ellen Kimberlite is a poorly exposed volcanic breccia located about northeast of Crystal Falls in the Upper Peninsula of Michigan. The first publication in 1981 describing the feature led to speculation that this or similar kimberlites in the area might have been the source of the diamonds discovered a century before in Wisconsin as well as a period of
Volcanic rock strictly metavolcanic rocks. Volcanic rocks are among the most common rock types on Earth's surface, particularly in the oceans. On land, they are very common at plate boundaries and in flood basalt provinces. It has been estimated that volcanic rocks cover about 8% of the Earth's current land surface. Volcanic rocks are usually fine-grained or aphanitic to glass in texture. They often contain clasts of other rocks and phenocrysts. Phenocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye. Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine