MISSOURI MOZARKITE, COAL & GEODES

I had the opportunity to live and work in northeastern Missouri during the early 90s.  The landscape was interesting with lots of deciduous trees and rolling hills.  The spring seasons were beautiful in that the forest was filled with blooming trees, shrubs and a variety of flowers.  The combination of flowering redbud and dogwood really livened up the landscape.  Towering above the smaller trees and shrubs were fairly large hickories and oaks.  Although almost all were second or third growth trees, occasionally a giant specimen indicated the loggers missed or ignored the individual.  I lived “in the country” and had a couple of these large specimens on my few acres---even at my age they were an enjoyment to climb, perch and contemplate life!

Northeastern Missouri is in a physiographic region termed the Dissected Till Plains (DTP).  In fact, the DTP extend south to the Missouri River (flowing west to east [Kansas City to St. Louis] through the middle of the state.  What this indicates is that the Missouri River is essentially an ice marginal stream---the great Pleistocene glaciers covered the northern half of the state but not the Ozark Plateaus south of the River.  The glacial till, composed of a variety of sediments from clay to boulders, varies in thickness (several hundred feet thick in ancient glacial valleys), and is being eroded and dissected by modern streams---hence, the rolling hills.

In some localities, a thin veneer of wind-blown loess (clay and silt size particles transported from glacial outwash plains) covers the till.  In northeastern Missouri the till usually sits on Pennsylvanian rocks composed of limestone, shale and sandstone, often of marine near shore, deltaic or swamp environments.  In fact, the area around Kirksville (my home for seven years) had a robust coal mining economy a century ago.  The small town of Novinger, about 10 miles west of Kirksville, was the center of mining activity and the Kirksville Daily Express (September 6, 2014) noted the “coal mines started making their way to Novinger during the late 1800s.  From 1880 to 1966 the city of Novinger was home to 57 coal mines in Adair County, which was labeled as the third largest producer of coal in the state in 1912 in a report done by the Missouri Bureau of Labor Statistics in 1914. Novinger was also the home to the Billy Creek Coal mine, the last deep-shaft mine in the state before it closed in January 1966.” Today the only references to the mines are scars of the Pennsylvanian rocks visible in openings of the till; at least that is all I could locate.  Some of the local population noted that several tunnels existed under the city---fact or fiction, I do not know.  

 

Postcard  of buildings at the Rombauer Coal Mine near Novinger.  Courtesy of: Novinger Planning Progress © 2003.

The area surrounding Kirksville was not exactly a hotbed of mineral and fossil collecting!  I sorted through some of the “gravel pits” looking for chalcedony and/or jasper.  Once I looked for rumored Lake Superior Agates  in a gravel pit along the Mississippi River two counties to the east—no luck.  The best (in fact great) mineral collecting was looking for the famed Keokuk Geodes a couple of counties east and one north around the small city of Keokuk, Iowa, across the River.  However, the Mississippian Warsaw and Keokuk formations also crop out on the Missouri side and offer the geodes.  These Mississippian rocks are older than the Pennsylvanian rocks exposed near Kirksville.

 

Keokuk-type Geode (width ~4.5 cm.) collected near Hamilton, Illinois.  Note secondary dolomite crystals on quartz lining.

Other than the Keokuk Geodes Missouri’s better known minerals probably are those associated with the Tri-State (Missouri, Kansas, Oklahoma) Lead and Zinc District (see posting 7/21/14) and the Lead Belt/Viburnum Trend in the southeastern part of the state (see details on 6/28/14 posting).

However, in visiting with lapidaries most could care less about the calcite, galena, etc. but mention Mozarkite and their eyes light up!  As a side note, I never understood something here.  If a locality where colonies of bees are housed are called apiaries and bee workers (human) are apiarists why are people working with polishing minerals not called lapidarists?

Mozarkite (MO:Missouri; ZARK:Ozarks;ITE:mineral) is not an officially recognized mineral but is a form of cryptocrystalline quartz.  I have seen it referred to as a variety of chert or flint or chalcedony.  Whatever your choice, the specimens are a swirling array of colors (often pastel in shade) notably purple, blue, brown, yellow, red, orange, salmon, white, and more and due to impurities such as iron, copper, manganese, nickel, etc.  Since it has a hardness of ~7.5 specimens take a high polish and are fashioned into a variety of cabochons and free forms for wire wrapping or setting in pendants.

  

Polished mozarkite nodule. Width ~4.0 cm.

Polished mozarkite nodule. Width ~3.0 cm.

According to Missouri lapidaries mozarkite is unique to the state and is only found in a few areas south of the Missouri River and west of the Lake of the Ozarks, most notably around the small town of Lincoln in Benign County.  It occurs in nodules (up to cobble and boulder size) weathering from the Cotter Dolomite of Ordovician age.  On a road trip when living in Missouri I stopped and searched a few road cuts and roadside ditches and gathered up a few smaller nodules.  Unfortunately, those became a causality of my several moves across the country.  However, I still have in my collection a couple of smaller pieces (purchased) that are nicely polished. I can understand why lapidaries are enamored with mozarkite.  In fact, the State Legislature also was enamored since in 1967 Senate Bill 216 designated mozarkite as the official Missouri State Rock.  I would have preferred state mineral; however, that slot was occupied by galena!