|
USA | |
|
| [var. Bitumen] Mahaffey, Nova, Finkelman, Robert B. (2022) The Extraordinary Variety and Complexity of Minerals in a Single Keokuk Geode from the Lower Warsaw Formation, Hamilton, Illinois, USA. Minerals, 12 (7) 914 doi:10.3390/min12070914 |
|
| [var. Bitumen] Robertson, Percival (1942): Bituminous matter in Warsaw geodes [abs.]: Transactions of the Ilinois State Academy of Science, v. 35, no. 2, p. 138-140.
van Tuyl, Francis M. (1923): Annual Reports for the Year 1921-22, Mississippian. The Stratigraphy of the Mississippian Formations of Iowa, Iowa Geological Survey, Annual Report, Volume 30 |
|
| [var. Bitumen] Freiburg, J. and Rakovan, J. (2012) The Conco Mine, North Aurora, Kane County, Illinois. Rocks & Minerals, 87, #2, 116-125. |
|
| Zeitner (1956), Midwest Gem Trails |
|
| Smith, Arthur E., Prior, Harold L. (2002) Iowa Mineral Locality Index. Rocks & Minerals, 77 (6) 404-413 doi:10.1080/00357529.2002.9924893 |
|
| Smith, Arthur E., Prior, Harold L. (2002) Iowa Mineral Locality Index. Rocks & Minerals, 77 (6) 404-413 doi:10.1080/00357529.2002.9924893 |
|
| [var. Bitumen] (1917) Useful minerals of the United States. Bulletin Vol. 624. US Geological Survey doi:10.3133/b624 |
|
| [var. Bitumen] Winslow, Arthur (1894) Lead and Zinc Deposits (Section 2). Missouri Geological Survey, Volume VII: 571. |
Keokuk, Lee County, Iowa, USA