1. Diamond Stories and Kimberlite Discovery in Wisconsin

2. The Wisconsin Diamond Story or It Ain’t Topaz
Mike Mudrey
University of Wisconsin-Extension
Emeritus

3. Diamonds in Wisconsin
Between 1876 and 1913, diamonds were found in at least seven localities in southern and central Wisconsin. All were found in Pleistocene gravel deposits or Holocene river gravel.
The bedrock kimberlite source for these diamonds is unknown, but was presumed to be in northern Canada, the only area north of Wisconsin previously known to contain kimberlite.

4. Bedrock Geology
Until the past twenty years, diamond exploration in the Upper Midwest has focused on the Precambrain. However, suggestive radiometric data and fossil-bearing dolomites clasts from the Lake Ellen locality, suggest that emplacement of midwest diamonds may be as young as Jurassic.
From S. Dutch, Univ. Wisconsin-Green Bay

5. Wisconsin Diamond Occurrences and relations to glacial end moraines
The twenty or so diamonds found in Wisconsin are generally found in the terminal moraines of eastern Wisconsin. Documentation on the Plum Creek locality in western Wisconsin is poor.

6. Vintage 1900 analysis of glaciogene origin of midwest diamonds (Hobbs, 1901)

7. Wisconsin Diamond Occurrences and relations to glacial end moraines
The twenty or so diamonds found in Wisconsin are generally found in the terminal moraines of eastern Wisconsin. Documentation on the Plum Creek locality in western Wisconsin is poor.

8. Eagle Area

9. Photograph of lead castings of Eagle (top) and Oregon (bottom) diamond
Photograph of lead castings of Eagle (top) and Oregon (bottom) diamond (Hobbs, 1901)
Photograph of lead castings of Eagle (top) and Oregon (bottom) diamond
The first documented diamond discovery in Wisconsin was made during the digging of a water well in 1876 in Eagle, Waukesha County of a carat stone. More on the history of this diamond later. The bottom photograph is of the diamond found near Oregon, Dane County of a 4.0 carat stone in The Eagle diamond was subsequently stolen, and the history of the Oregon diamond subsequently acquired by Tiffany and Co of New York is not known.

10. Acquisition Card- American Museum of Natural History
After purchasing the Eagle diamond, J.P. Morgan donated the gem to the American Museuim of Natural History. On the evening of October 29, 1964, the Museum was broken into and the Eagle and other gems were stolen. The thief was apprehended by February 1965, however the Eagle diamond was not recovered.

11. Acquisition Card- American Museum of Natural History
!!!!! Stolen Oct !!!!!
After purchasing the Eagle diamond, J.P. Morgan donated the gem to the American Museuim of Natural History. On the evening of October 29, 1964, the Museum was broken into and the Eagle and other gems were stolen. The thief was apprehended by February 1965, however the Eagle diamond was not recovered.

12. Saukville
Burlington

19. Antigo micro-Diamond Discovery by Al Falster
The twenty or so diamonds found in Wisconsin are generally found in the terminal moraines of eastern Wisconsin. Documentation on the Plum Creek locality in western Wisconsin is poor.
Now in Weeks Hall Museum

20. M.G. Mudrey, Jr. Wisconsin Geological and Natural History Survey
Use of High-Resolution Aeromagnetic Data for Regional Geology Investigations, Southeastern Wisconsin (Where’s the Kimberlite!)
M.G. Mudrey, Jr.
Wisconsin Geological and
Natural History Survey
Presented at the 1998 Institute on Lake Superior Geology, Minneapolis, Mn
Presented at the 1998 Institute on Lake Superior Geology, Minneapolis, Mn

21. Diamonds in Wisconsin
Between 1876 and 1913, diamonds were found in at least seven localities in southern and central Wisconsin. All were found in Pleistocene gravel deposits or Holocene river gravel.
The bedrock kimberlite source for these diamonds is unknown, but was presumed to be in northern Canada, the only area north of Wisconsin previously known to contain kimberlite.

22. Vintage 1900 analysis of glaciogene origin of midwest diamonds (Hobbs, 1901)

23. Photograph of lead castings of Eagle (top) and Oregon (bottom) diamond
Photograph of lead castings of Eagle (top) and Oregon (bottom) diamond (Hobbs, 1901)
Photograph of lead castings of Eagle (top) and Oregon (bottom) diamond
The first documented diamond discovery in Wisconsin was made during the digging of a water well in 1876 in Eagle, Waukesha County of a carat stone. More on the history of this diamond later. The bottom photograph is of the diamond found near Oregon, Dane County of a 4.0 carat stone in The Eagle diamond was subsequently stolen, and the history of the Oregon diamond subsequently acquired by Tiffany and Co of New York is not known.

24. Acquisition Card- American Museum of Natural History
After purchasing the Eagle diamond, J.P. Morgan donated the gem to the American Museuim of Natural History. On the evening of October 29, 1964, the Museum was broken into and the Eagle and other gems were stolen. The thief was apprehended by February 1965, however the Eagle diamond was not recovered.

25. Saukville (l) and Burlington (r) from USGS Circular 842
The whereabouts of two Wisconsin diamonds are known, and as late as the 1980s were public ally displayed. The Saukville is a 6.57 carat stone found in 1881, and the Burlington, near the Kenosha kimbelite, a 2.11 carat stone in

26. Wisconsin Diamond Occurrences and relations to glacial end moraines
The twenty or so diamonds found in Wisconsin are generally found in the terminal moraines of eastern Wisconsin. Documentation on the Plum Creek locality in western Wisconsin is poor.

27. Kimberlite Discoveries
With the discovery of the Lake Ellen kimberlite in Iron County, Michigan, Cannon and Mudrey (1981) suggested the drift diamonds in Wisconsin may have come from a more local source.
Carlson and Adams (1997) described a kimberlite in Kenosha , southeastern Wisconsin, which was defined by magnetics and drilling to be about 280 m across.

28. http://pubs.er.usgs.gov/pubs/cir/cir842 USGS Circular 843
In 1981 Cannon and Mudrey published a summary of the Wisconsin diamond discoveries and a kimberlite body identified in northern Michigan. This USGS Circular is available on line at They discussed all of the known diamonds found up to 1981, and the preliminary geology of the Lake Ellen kimberlite.

29. Map showing the location of diamond discovery sites, marginal moraines of major ice lobes and direction of ice movement, possible cryptovolcanic structures and the Lake Ellen kimberlite from USGS Circular 842
Map showing the location of diamond discovery sites, marginal moraines of major ice lobes and direction of ice movement, possible cryptovolcanic structures and the Lake Ellen kimberlite from USGS Circular 842
As part of their analysis, Cannon and Mudrey documented possible cryptovolcanic features in the Upper Midwest. Most of these are now interpreted as meteorite impact structures.

30. Bedrock Geology
Until the past twenty years, diamond exploration in the Upper Midwest has focused on the Precambrain. However, suggestive radiometric data and fossil-bearing dolomites clasts from the Lake Ellen locality, suggest that emplacement of midwest diamonds may be as young as Jurassic.
From S. Dutch, Univ. Wisconsin-Green Bay

31. Diamonds and Kimberlite in Wisconsin
In the 1980s, detailed aeromagnetic data were acquired as part of a proprietary mineral exploration program in southeastern Wisconsin. That information lead to the identification of high-frequently, short wavelenth anomalies in Kenosha and Ravine Counties. US Department of Energy aeromagnetic/aeroradioactivity surveys also covered southeastern Wisconsin, and as an aside, there are several high-frequency spikes on the 10-km spaced flight lines. The work of Robert Patenaude in the mid 1960s was not sufficiently detailed to analyze for similar features.

32. Diatreme Outline

33. Aeromagnetic Map, Pleasant Prairie
The 800-m spaced flight lines identified a small, high-frequency anomaly in the western part of the City of Kenosha, Wisconsin near the intersection of Interstate 94 and State Highway 50. The Patenaude Survey of 1965 was along the Interstate and did not identify any anomalous signatures. Simiarly, the NURE/DOE Survey in 1980 along the north section line of Section 6 (County K) similarly did not identify an anomaly. These lines were about 800-m west and north of the kimberlite.

34. Details of Pleasant Prairie Kimberlite Anomaly

35. Line profiles
Carlson and Adams (1997) reported on the drilling of the less than 100-gamma anomaly at ILSG in Sudbury. The Six-Pack diatreme, as they termed this body, is a melnoite with clasts of fossiliferous dolostone and red, bedded arenites, and is diamond bearing. Their work is the first recorded mantled-sourced diatreme to be identified in southeastern Wisconsin, and raised the significant possibility that Wisconsin and possibly other midwestern diamonds originated in Wisconsin or even father to the south..

36. Aerial photograph of kimberlite site
The society/environmental problem of this discovery is illustrated with this aerial photograph of the site. The west edge is Interstate 94, the southern edge is State Highway 50. Also shown is a large commercial grocery store (arrow). Also a subdivision about 1/8 mile east of the kimberlite locality is shown by the meandering roads system.

37. Photograph of kimberlite site, notice houses in background
This photograph over the kimberlite shows the housing development to the east.

38. Summary and Conclusions 1
Flight-line spacing greater than 800 m will be ineffective in the identification of small, highly magnetic kimberlite.
Because of weak intensity, aeromagnetic anomalies from kimberlite will only be evident where regional gradients are subdued and regional anomalies are weak.

39. Summary and Conclusions 2
Other kimberlitic bodies may occur in Wisconsin and Illinois and may be the source for midwest diamond discoveries.

40. Summary and Conclusions 3
Urbanization in the Milwaukee-Chicago corridor may discourage further geologic and geophysical analysis and competing land-use may make further exploration and ultimate development difficult.