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Boley agates

Last Updated: 8th Nov 2010

About fifty miles east of Norman, Oklahoma - where I currently live - there's a north-south trending formation characterized by a reddish-brown conglomerate out of which is weathering a chert breccia known locally as "Boley agate." The small town of Boley in Okfuskee County is more or less the northern terminus of this formation, which extends southward for about forty-five miles, petering out somewhere north of Ada. The sites where I collect Boley agates are mostly in Seminole County, a few miles west of Sasakwa on Oklahoma highway 56.

The material is quarried as gravel and is used for surfacing the section-line roads in the area, and also shows up in the central Oklahoma area in such landscaping contexts as the gravel islands in parking lots.

There are quite a few web references to Boley agate, but relatively little solid information. They come from a member of the Francis Formation known as the Nellie Bly, which is known to be of Pennsylvanian-Period age. The conglomerate in which they're embedded consists mostly of quartz sand from the Ouachita/Ozark uplift to the east: this was a near-shore depositional environment. The formation is fossiliferous, and its fauna have been described in Oklahoma Geologic Survey Bulletin No. 74 (Geology of Seminole County, Wm. F. Tanner, 1956). Tanner makes only a passing reference to the chalcedony content of the formation, and no mention at all of the feldspar (which I think is likely to have originated in the Arbuckle fold belt to the south).

Because of their rich variation and the complex fracturing/cementation history recorded in them, these agates seems to me to merit more attention from the geologic community than they've received. Aside from a few such references as the listing in the University of Nebraska's Agate Database (http://snr.unl.edu/data/geologysoils/agates/agatedatabase.asp), these engaging rocks seem to have gone mostly unnoticed, except by collectors.

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Thanks for sharing!

Dave Crosby
12th Feb 2011 8:08pm

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