|
USA | |
| [Chalcedony var. Agate] Horick, P.J. (1974) The Minerals of Iowa. Iowa Geological Survey Educational Series 2, 88 pages. |
| 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 |