Seventy-eight diamonds recovered from weathered kimberlite from diatremes in the Colorado-Wyoming State Line district are described in terms of size, weight, morphology, color, fluorescence, and inclusions. The stones are subdivided into two groups: small diamonds, those approximately >1 mg and >1 mm; and microdiamonds, those ≤1 mg and ≤1 min. Total combined weight of all diamonds in both groups is about 84 mg. (0.42 carat). Octahedral forms are most abundant in the microdiamond fraction and octahedra/dodecahedra ratios show a general decrease with size (O/D = 6.0 for <0.3–1.0 mm range and 1.2 for 1.0->2.0 mm range). Octahedra and macles appear to be primary growth forms, and dodecahedral forms evolved from octahedra. Variations in size and form are reflected by weak to moderate trends in color, fluorescence, and inclusion content.

Research Article| August 01, 1976 Diamond in kimberlitic diatremes of northern Colorado M. E. McCallum; M. E. McCallum 1Department of Earth Resources, Colorado State University, Fort Collins, Colorado 80523 and U.S. Geological Survey, Denver Federal Center, Denver, CO 80225 Search for other works by this author on: GSW Google Scholar C. D. Mabarak C. D. Mabarak 2Department of Earth Resources, Colorado State University, Fort Collins, Colorado 80523 Search for other works by this author on: GSW Google Scholar Author and Article Information M. E. McCallum 1Department of Earth Resources, Colorado State University, Fort Collins, Colorado 80523 and U.S. Geological Survey, Denver Federal Center, Denver, CO 80225 C. D. Mabarak 2Department of Earth Resources, Colorado State University, Fort Collins, Colorado 80523 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1976) 4 (8): 467–469. https://doi.org/10.1130/0091-7613(1976)4<467:DIKDON>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. E. McCallum, C. D. Mabarak; Diamond in kimberlitic diatremes of northern Colorado. Geology 1976;; 4 (8): 467–469. doi: https://doi.org/10.1130/0091-7613(1976)4<467:DIKDON>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Small diamonds have been recognized in concentrates from deeply weathered kimberlite from diatremes in northern Colorado. This discovery represents the first authenticated occurrence of diamonds in Colorado and the second authenticated occurrence of diamonds from weathered kimberlite in North America. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.