Events

Welcome to the Colorado Chapter of the Friends of Mineralogy

November  Meeting – Thursday, Nov. 16, 2017, 7:30 pm

Ed Pedersen, long time collector with Art Smith who specialized in Arkansas phosphate minerals will be giving a presentation on the “Phosphate minerals of Arkansas and where we found some.

 Meeting at Denver Museum of Nature and Science, 2001 Colorado Blvd, City Park, Denver – VIP Room (1st floor). Enter the museum on the north side, through the security/staff entrance to the left of the main entrance.

There will be a FMCC board meeting on Thursday at 6.30 PM.

Presentation Abstract

Phosphate minerals of Arkansas and where we found some

 

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Strengite and Kidwellite from Three Oak Gap, Polk Co., Arkansas, USA. Photograph courtesy of Tom Loomis, Dakota Matrix.

Ed  Pedersen

Arkansas has produced a large number of phosphate mineral specimens.  Nearly all of the iron and aluminum  phosphate minerals of interest occur in or adjacent to the Ouachita Mountains.  The dominant rock in the area is the Arkansas Novaculite of Devonian and Lower Mississippian age.  It reaches a maximum thickness of 900 feet and is overlain by the Stanley Shale.  Most of the Iron Phosphates, such as strengite and kidwellite, are found in fractured novaculite.  The novaculite is underlain by the Missouri Mountain Slate and the Blalock Sandstone which do not contain any minerals of interest.  Below these are the Polk Creek Shale and the Bigfork Chert which are the host rocks for the aluminum phosphates such as wavellite and variscite.

One locality has produced many of the better iron phosphate specimens.  The fracture zones in the novaculite seem to be more extensive and more highly mineralized at the Coon Creek Mine than at most Arkansas localities.  Many of the better specimens of kidwellite, rockbridgite, strengite, and phosphosiderite, especially those offered by dealers, have come from this locality.

During the 1970s and 1980s an informal group of mineral collectors calling themselves The Coon Creek Mining and Recreational Society met once a year to collect Arkansas minerals.  This group consisted of A. L. Kidwell, Art Smith Jr., Henry deLinde, Meredith York, Mike Howard, Charles Steuart, Don Owens, and Dr. Buford Nichols. Since both Art Smith and Al Kidwell were members of the Mineral Study Group of the Houston Gem and Mineral Society and Arkansas was the closest strongly mineralized area to Houston, collecting efforts were focused there and the phosphate minerals were included.

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About Ed Pedersen:

Edward Pedersen is a geologist with a BS in Geology from the University of Nebraska, Lincoln, Nebraska and a MS in Geology from Arizona State University, Tempe, Arizona. During his professional career he has worked as a Geophysicist for more than 20 years with Amoco Production Company, in Houston and Denver. Later, he advanced his skill sets as a ground water geologist with the Nebraska Department of Environmental Quality, and as a geologist-geophysicist with an Environmental Consulting Firm in Denver.

He has been interested in collecting fossils since grade school, but started collecting minerals in 1965 after taking mineralogy courses in college. He has done extensive field collecting in Arizona, Texas and Arkansas. While living in Houston., he has been Chairman of the Mineral Section of the Houston Gem and Mineral Society and been a member of  Friends of Mineralogy since early 1970s. Other clubs he has been or is a member of include the Lincoln Nebraska Gem and Mineral Club (Mineral Study Group leader), North Jeffco Gem and Mineral Society and the Rocky Mountain Micromineral Association, serving at one time as the Program Chairman.