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  • FL conglomerate

    What is the Composition of Conglomerate?

    Conglomerate can have a variety of compositions. As a clastic sedimentary rock, it can contain clasts of any rock material or weathering product that is washed downstream or down current. The rounded clasts of conglomerate can be mineral particles such as quartz or feldspar, or they can be sedimentary, metamorphic, or igneous rock fragments. Clasts of quartzite, sandstone, limestone, granite, basalt, and gneiss are especially common. The matrix that binds the large clasts together can be a mixture of sand, mud, and chemical cement.
    Conglomerate-Forming Environment: A beach where strong waves have deposited rounded, cobble-size rocks. If buried and lithified, these materials might be transformed into a conglomerate. Image © iStockphoto / Jason van der Valk.

    Conglomerate-Size Sediment Clasts: Pebble-size clasts of many compositions deposited together on a beach. Quartz, sandstone, and limestone clasts are all easily recognizable. Largest clast is about two inches (five centimeters) across. Image © iStockphoto / Ivan Ivanov. How Does Conglomerate Form?

    Conglomerate forms where sediments of rounded clasts (pieces..) at least two millimeters in diameter accumulate. It takes a strong water current to transport and produce a rounded shape on particles this large. So the environment of deposition might be along a swiftly flowing stream or a beach with strong waves. These conditions might only be met during times of extreme flow or wave action. However, it is during these times that much of the Earth's sediments are moved and deposited.

    To form a conglomerate, there must also be a source of large-size sediment particles somewhere up current. The rounded shape of the clasts reveals that they were tumbled for some distance by running water or moving waves. These conditions are found in streams and standing water bodies in many parts of the Earth.
    Conglomerates often begin when a sediment consisting mainly of pebble- and cobble-size clasts is being deposited. The finer-size sand and clay, which fill the spaces between the larger clasts, is often deposited later on top of the large clasts and then sifts down between them to fill the interstitial spaces. After compaction, the deposition of a chemical cement then binds the sediment into a rock

    In FL conglomerates form from limrock and quartz cemented together with silica (chert) and makes for some wacky looking points. I do not think it works easily due to the different materials composing it.
    Professor Shellman

  • #2
    Tom at first glance that point looks like it was knapped from asphalt...
    The chase is better than the catch...

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    • #3
      Tom - I have to agree with Frank. It looks like asphalt with embedded limerock they use on our secondary roadways. I can just see a NA trying to knap that stuff and cussing his head off or whatever they did when they got frustrated. :- )
      Pickett/Fentress County, Tn - Any day on this side of the grass is a good day. -Chuck-

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      • #4
        LOLOL other side looks like asphalt, too. Such and odd and actually rare material here. They had coral and chert so to make one out of this material was an oddity. I bet the maker was intrigued and thrilled. There's a tiny bit of sandstone "rind" on the right side... This material must occur within sandstones and not limerock like chert and agate do. Woodland. Pinellas Co. Manasota Culture.
        Last edited by tomclark; 02-13-2018, 10:51 AM.
        Professor Shellman

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        • #5
          That is a cool piece. There are some interesting conglomerates and points made from them across this country. Thanks
          Searching the fields of Northwest Indiana and Southwestern Michigan

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          • #6
            Tom following all your posts and your reactions to others I am really learning some interesting facts here .
            It’s almost like Fl is a whole different world and language .
            You have the beautiful agatized coral then these pieces that are stuck to sandstone or limestone deposits .
            That asphalt lithic is crazy . Totally get how one part would be hard then soft reading mineral books . Amazing how the person even knapped it .
            See how easy we have it in S Georgia . There is Chert , jasper , and more Chert . It’s the quartz I like but it doesn’t seem to survive unless it makes it to that glass stage .

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