Saturday, May 30, 2015

Missouri State Rock - Mozarkite

published on: 2/28/2003

Contributing Teacher(s): Calene Cooper

Subject Area: Science/Life

Grade Range: Middle Grades (6-8)

Materials Needed:

  • several samples of Missouri rocks
  • dilute hydrochloric acid or vinegar
  • small pieces of glass or baby food jars
  • nails

Process Standards:

  • Goal 1.1 develop questions and ideas to initiate and refine research
  • Goal 1.2 conduct research to answer questions and evaluate information and ideas
  • Goal 1.3 design and conduct field and laboratory investigations to study nature and society

Content Standards:

  • Science 1. Properties and principles of matter and energy
  • Science 3. Characteristics and interactions of living organisms
  • Science 5. Processes (such as plate movement, water cycle, air flow) and interactions of earth’s biosphere, atmos...

    Time Allowance: 1 class period

    Description: This lesson from a six lesson unit deals with the Missouri Symbol of Mozarkite.

    Comments: This lesson is one of six lessons of a complete unit.

    Classroom Component: Teacher Note: This lesson is a part of a complete unit. Click on the links below to view other individual lessons. Lesson introduction page State Flower--Hawthorn State Fish--Catfish State Aquatic Animal--Paddlefish State Mineral--Galena State Tree Nut--Black Walnut Background Information: With the exception of the granite mountains found in Central Southeast Missouri, almost all other Missouri rocks will be sedimentary rocks and this key will help you identify the 14 major rocks of our state. Explore with your students the uses of these rocks and their impact on Missouri''s economy.

    Background Information on Missouri State Rock - Mozarkite

    The formation of mozarkite and all cherts is a part of our state''s geologic history. The history begins with the formation of limestone and sandstone under the ancient shallow seas that once covered most of our state. As early as Cambrian times (600 m.y.a.) and possibly earlier, thick deposits of limestone were laid down in our state by countless marine animals and plants that lived and died in this "mid-American sea". The marine animals included Foraminifera, tiny sand-grain sized one-celled protozoa. Foraminifera formed shells of limy (calcium-bearing) material and lived from before Cambrian times to today. Larger animals that formed fossils seen all over Missouri include crinoids, worms, corals, bryozoans and molluscs. All of their shells were made of CaCO2. Sand or silica (SiO2) was eroded and transported down into the sea by rivers from its original igneous beds of Pre-Cambrian granite. The calcite that formed calcium carbonate was transported from the land as well. As the sea water became saturated with calcium carbonate and silicon dioxide, these compounds settled to the bottom and formed layers of limestone, dolomite (another form of limestone with manganese from erosion) and sandstone. Shales and other sedimentary rock layers formed. By Ordivician times (500 m.y.a.) our whole state was submerged beneath the sea. For the next 250 million years our state was uplifted by tectonic forces that left it dry land only to be re-submerged several times. Sedimentary rock layers continued to form leaving behind a detailed history of Missouri during the Paleozoic era. By Permian times (270 m.y.a.) our state was dry land again and the sea was gone (permanently?). Now the forces of weathering, erosion and transportation began to shape our state.

    Meanwhile, under the layers of sedimentary rock, the various chemical solutions such as CaCO2, SiO2, MgCa(CO3)2) deposited and hardened into various rock types. One kind, chert, chemically replaced layers of limestone and dolomite or it precipitated out of the mixture of compounds in the sea. Chert is cryptocrystalline quartz (SiO2) which means that the crystals of quartz that comprise it are too small to be seen with the naked eye. Layers or bands of chert formed between layers of Missouri''s ever present limestone and dolomite. It can easily be seen today in roadcuts as bands of off-white or light gray layers. The forces of erosion remove the chert from the softer limestone but since chert is much harder it does not weather as fast. Some chert rocks are worn smooth as pebbles in our common streams and became a valuable source of gravel for construction and landscaping. Chert comes in many colors but usually it is white, tan or gray. Secondary coloration is sometimes picked up by iron deposits that give it a red, pink or orange color and by the action of plant life in rivers that stain it green or black. To determine the true coloration of the chert it should be broken so that the inside is exposed.

    Some cherts of different colors can form under special circumstances if they were precipitated in the presence of iron oxides, clays and other minerals. These cherts show pastel colors throughout their matrix and this can be called flint, jasper, or mozarkite. As is true for all cherts, mozarkite has a hardness of 7 to 7.5, a density of ~2.65 g/cm3, and consists of 95-99.5% silica. Mozarkite is brittle with a splintery or conchoidal fracture and can be found in the Missouri Ozarks as nodules, "lenses" or still in beds of limestone. It is usually associated with fossils and can contain some marine fossils although not as frequently as in the beds of dolomite in which mozarkite is found. Much chert and mozarkite is found today in typical Missouri red clay and sandy soils. In certain areas of our state, when roadcuts are made, new finds of Mozarkite are uncovered.

    Mozarkite comes in all colors, pink, brown, purple, rose, and wine predominating. The imaginative eye sees patterns showing pictures of scenes, faces, and wildlife in the polished stones. The pastel colors in this special form of chert are the result of minor impurities in this crptocrystalline silica An analysis of these impurities show the following results:

    Silica Si High Aluminum Al Low
    Iron Fe Present Manganese Mn Low
    Titanium Ti Trace Calcium Ca Not detected
    Magnesium Mg Low Sodium Na Low
    Potassium K Low Copper Cu Trace
    Boron B Trace Nickel N Trace
    Silver Ag Trace

    Mozarkite can be polished through lapidary processes to create exceptional beautiful gem quality stones. These polished stones can be made into pendants, cabochons, polished slabs, book ends, and belt buckles to name a few. Mozarkite is a popular gem quality stone collected by rockhounds and lapidaries. While it may occur throughout the Oscar region of our state, there have been only a few abundant deposits found. The major area for finding mozarkite is in Benign County around the city of Lincoln. Smaller deposits are known from south of St. Louis and in Labeled County near Lebanon.

    Legends of Mozarkite

    Native Americans may have valued this colored chert as a special form of flint used for making points. Flint is another form of chert and so the properties of mozarkite would have allowed it to be used in this way. In the Indian legend of Tam Sack Mountain and Mine Sack Falls, it is possible that mozarkite played an important role. The Piankeshaw Tribe inhabited the region around the St. Francis River and the igneous granite mountains of southeast Missouri. A yearly custom among the Piankeshaws was to row their canoes up the Mississippi to the Missouri and as far west as the Osage River (present day Lake of the Oscar). Here they traded with the Osage Indians near Warsaw in Benton County. One valued article for trade was a colored chert which the Osage traded with tribes all over North America. The location of the O

    For additional information contact :
    Calene Cooper
    West Jr. High
    Columbia 93
    (573) 886-2760

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