Saturday, March 23, 2013

KANSAS MINERALS: EAST



Kansas is a state with abundant fossil and mineral resources, but with few specimens that rockhounds would consider gemstones or even semi-precious gemstones.  However, there are some very collectable specimens available for most mineral enthusiasts.  The problem usually associated with collecting in Kansas is that virtually all land is privately owned and/or state land that is off-limits to collecting.  On the other hand, residents of Kansas are nice people and often will give permission to rockhounds for admittance to property.  The major exception to this possibility is with the collecting of vertebrate fossils.  In the last couple of decades landowners have found that vertebrate fossils may be valuable monetary resources—items worth hundreds or thousands of dollars to interested buyers.  So, beware of this fact and be on your best behavior---ask permission before entering land. 
            
The eastern one-half of the state has numerous outcrops of late Paleozoic sedimentary limestones and shales and these rocks hold tremendous numbers of invertebrate fossils, many of which (Orders, Families) became extinct during the great end-of-Permian extinction event (~ 252 Ma).  The western part of the state is home to Cretaceous and Cenozoic sedimentary rocks and sediments with their vast resources of both vertebrate and invertebrate fossils, as well as interesting minerals.  As with the Paleozoic, the end of the Mesozoic (~65.5 Ma) had a large-scale extinction event. 


Generalized geologic map of Kansas.  The eastern one third of the state has bedrock of Mississippian, Pennsylvanian and Permian age (blues and purples). Outcrops of Cretaceous rocks (green) and Cenozoic (yellow, tan and brown) dominate in the western section.  Map from Kansas Geological Survey. 
 This posting will focus on collectable minerals from the state and leave the fossils for another story.  However, it often is not possible to collect minerals without noticing the fossils!


Diagram showing emplacement of kimberlite pipes.  Courtesy of Kansas Geological Survey.
Outside of a few scattered kimberlite pipes of igneous rocks in eastern Kansas, the surficial rocks in the state are either sedimentary or unconsolidated sediments.  Kimberlites are of special interest since olivine–rich magma was “shot” upwards from deep in the earth’s crust, perhaps as deep as 100 miles and traveling ~1200 feet per second (Kansas Geological Survey, 2000).  Many well-known kimberlite pipes are located in South Africa where they are the site of major diamond discoveries/production.  No diamonds have been located in the Kansas pipes; however, thousands of diamonds have come from similar pipes in the Colorado-Wyoming State Line Diamond Belt.  All other igneous rocks, with their vast array of interesting minerals, are far below in the Kansas subsurface.

At one time, before the current trend for diamond exploration, I was able to collect hundreds of small red pyrope garnets from the Stockdale pipe in Riley County, north of Manhattan (Meyer and Brookins, 1976).  I am uncertain about current access but rockhounds could check with the Geology Department at Kansas State University.  


Galena cubes on chert with minor sphalerite and chalcopyrite collected from near Galena, Kansas, in 1960’s.
Perhaps the best known mineral deposits in the state are located in extreme southeastern Kansas—and northeastern Oklahoma and southwestern Missouri—the Tri State Mineral District of the Ozark Plateau.  Galena (lead ore; PbS) was discovered in Missouri in the 1830’s and the mines were coveted by both sides during the Civil War.  In the 1870’s lead ore was discovered in Kansas and production of both lead and zinc (sphalerite; ZnFeS) continued for a century.  The Kansas Geological Survey (2001) noted that the Tri-State District, with more than 4000 mines, produced in excess of 23 million tons of zinc concentrates and four million tons of lead concentrates—50% of the zinc and 10% of the lead in the U. S.  The mining also left behind tremendous environmental damage and the U.S. Government has literally purchased and closed several towns in the region.  Growing up in Kansas we were informed in school, somewhat facetiously, that the tallest mountains in the state were the “chat piles” (overburden composed of chert, limestone and dolomite and a variety of bad things”, like cadmium) in southeastern Kansas.  On the plus side the region has produced spectacular mineral specimens of galena, sphalerite, dolomite, and chalcopyrite that occupy museum cases around the world.  Unfortunately, most mines no longer allow collecting and those of us who had the chance to collect in the 1960’s highly value our specimens.

“Black-jack” sphalerite (large dark mass and small crystal), dolomite crystals (white), and scattered chalcopyrite crystals (on dolomite).  Collected from near Galena, Kansas, in 1960’s.
The Flint Hills are a major topographic high extending north-south through Kansas and south into Oklahoma (Osage Hills).  The rocks holding up the Hills are of Permian age and consist of numerous beds of alternating marine limestones and shales.  The limestones contain uncountable nodules and beds of flint or chert.  As rainwater percolates through the surficial vegetation a weak acid is formed and this in turn begins to dissolve the limestone.  Since the flint/chert (a form of microcrystalline quartz) is rather insoluble the residue left behind is a cherty soil or cherty gravel and thus hinders erosion; hence, the rugged topography prevails.  The hills have not been broken by the plow and contain the largest tall grass prairie in the United States (see Tallgrass Prairie National Preserve). 


Permian limestone with scattered flint nodules and flint layers exposed along I-70 Riley County, Kansas.
One of the mysteries associated with the flint, at least to me, is “what is the origin of the silica”?  Some geologists believe marine creatures with skeletons of silica “died” and fell to the ocean floor and accumulated.  Others believe that some sort of water chemistry produced the silica.  Whatever the case, it is an interesting question.


Chase County Courthouse in Cottonwood Falls, Kansas.  The native building stone is the Permian Cottonwood Limestone, one of the many Permian building stones quarried in Kansas.
The rocks of the Flint Hills contain a fantastic array of Permian marine fossils such as brachiopods, bryozoans, corals, and some of the latest known trilobites.  The rocks also produce some beautiful building stones and many of the old eastern Kansas county courthouses, the buildings at Fort Riley, and early farm homes are constructed of local stone.. Of interest to rockhounds is the fact that some of the limestones contain geodes filled with (mostly) calcite, chalcedony, quartz and occasionally celestite.  I have collected numerous geodes from the Winfield Limestone, Dickinson County, in roadside ditches along KS 18 north of Chapman.  The Kansas Geological Survey (2005) suggests prospecting “near the town of Rock [Cowley County], along the Walnut River in Cowley County; north of the town of Douglass in Butler County; in Riley, Marshall, and Chase counties and … in a road cut ¼ mile west of Chapman, on 4th Street”.

Cut geodes with a calcite rind and calcite crystals in hollow center.  Collected from Winfield Limestone.
 The Osage Cuestas, east of the Flint Hills, cover the eastern part of Kansas south of I-70.  The underlying bedrock is composed of limestones and shales of Pennsylvanian age; however, they differ from similar looking rocks in the Flint Hills in that they are devoid of the flint and chert. These beds dip gently to the west with the land surface following the dip slope; the limestone beds hold up escarpments or cuestas on the east flank.  As in the Flint Hills, the rocks hold a variety of marine organisms and fossils are plentiful.  Perhaps the best locations to collect are in road cuts along secondary roads.

North of I-70 from Manhattan east to Kansas City the underlying Permian and Pennsylvanian strata are covered by widespread glacial drift resulting from incursions of the large northeastern U.S. continental glacier.  The main event (in Kansas), perhaps on the order of 600 ka, left behind various thicknesses of silt, clay, sand and gravel along with scattered boulders (termed glacial drift).  Some of the erratics in the drift may be traced to their source area with great accuracy.  Two of the easily identifiable cobbles came from outcrops of the Precambrian Sioux Quartzite (red quartz arenite, a sedimentary “quartzite”) near Sioux Falls, South Dakota and the Duluth “Gabbro” (dark-colored igneous rock from near Lake Superior).  There are several internet sites that talk about the presence (see www.findingrocks.com) of Lake Superior Agates in the drift; especially in gravel pits near McLouth north of Lawrence.  I have never seen these specimens but do not doubt their existence.
In south central Kansas is an area bordering Oklahoma termed the Red Hills.  Most visitors to the state would not recognize this landscape as being part of “flat” Kansas.  Late Permian red shales, siltstones and sandstone are eroded into a variety of tables, buttes and mesas often capped with beds of gypsum and/or dolomite.  The area also has numerous sinkholes as subsurface salt (halite) and gypsum have dissolved leaving a void and then collapsing.  These rocks in the Red Hills represent the “drying up” of the vast, latest Paleozoic, restricted circulation sea. It is fairly easily to collect specimens of rock gypsum and/or anhydrite.



Halite cube collected from Hutchinson salt bed in 1950’s.
Halite, or table salt, is a very common mineral in Kansas; however, since the mineral dissolves in “water”, outcrops are essentially non-existent and all beds are in the subsurface.  In fact, one of the largest halite deposits in the world is known as the Hutchinson salt bed, up to 400 feet thick and covering 37,000 sq. miles (Kansas Geological Survey; 1999).  The beds have been mined for several decades.
 
My fifth grade school trip was to the salt mines at Hutchinson where we wandered around underground without hardhats picking up pieces of halite.  In today’s world a fifth grader would not even get close to a working mine let along be taken down unprotected in a steel-cage elevator.  One small piece of halite remains from this little excursion by my class of 15 or so students.  The mine is still in use today and produces rock salt.  Perhaps more interesting to the rockhound is the Kansas Underground Salt Museum where visitors actually tour the caverns at 650 feet below surface level.

Eastern Kansas will surprise first-time visitors who have these visions of a flat landscape devoid of vegetation!  And, there are a variety of rocks, minerals, and especially fossils available for the collectors. 

REFERENCES CITED
Berendsen, P., T. Weiss and K. Dobbs, 2000, Kansas Kimberlites: Kansas Geological Survey Public Information Circular 16.

Brosius, L. and R. S. Swain, 2001, Lead and Zinc Mining in Kansas: Kansas Geological Survey Public Information Circular 17.

Kansas Geological Survey, 1999, Arkansas River Lowlands and Wellington-McPherson Lowlands; Rocks and Minerals:  www.kgs.ku.edu/Extension/lowlands/AL_factsheet1.pdf

Kansas Geological Survey, 2005, Flint Hills; Rocks and Minerals: http://www.kgs.ku.edu/Extension/flinthills/rocks.html

Meyer, H. O. A, and D. G. Brookins, 1976, Sapphirine, Sillimanite, and Garnet in Granulite Xenoliths from Stockdale Kimberlite, Kansas: American Mineralogist, v 6.

5 comments:

  1. iwant to find a rock finding place in ks

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  2. I live on my own private property! I have found a very very large amount of see through black ore. My Mother took it to PA and was stated this is more than you think!!!!!! In some cases, it appears to be orange, brown, or purple! Could just be the way the light hits it! Definitely see through! What is this? You can't break it with a hammer or any other object which tends me to believe this is more than I thought!!!!!

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    Replies
    1. its probably a diamond. it takes diamonds to break diamonds.

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  3. I found fern fossil crystal today. What would be the interest?

    ReplyDelete