The diatom collection at the University of Colorado Museum of Natural History is drawn from a variety of sources. It contains uncleaned and cleaned material, as well as permanent slides and material mounted for scanning electron microscopy.
The collection has two distinct origins. An historical collection contains material from a variety of exsiccatae distributed in the 19th and early 20th centuries, primarily those of Rabenhorst and Tilden, as well as others. This is primarily uncleaned material.
The second source is from J.P. Kociolek, and includes his personal collection. This is primarily freshwater, including fossil and modern samples. The collection is worldwide in scope, but has strengths in Great Smoky Mountains National Park, Colorado, the northern portion of the lower peninsula of Michigan (the environs of the University of Michigan Biological Station), lakes and rivers across the western United States and Hawaii. Samples from outside the United States include all continents, with strengths from Asia and Africa. There is material from nearly all the sites to accompany the slides.