Hunting this EarthCache will bring you to the roadside final resting place of many thousands of tiny prehistoric creatures. For millions of years, the area we now call Florida was covered by oceans. During this time sea creatures such as snails, clams, corals, sea urchins, sand dollars, fish, and others, lived and died. Their remains slowly built up layers of sediment thousands of feet thick. These sediments are the limestone, shell, and dolomite formations that are mined today. Limestone is a sedimentary rock which is more than 50% calcite (calcium carbonate, CaCO3) and dolomite (calcium magnesium carbonate, CaMg(CO3)2). It can vary widely in consistency and hardness. In Florida it can be found as a soft chalky material with microfossils, a hard recrystalized mass, a grainy sand-lime mass, or a fossiliferous mass. In some areas of Florida, the limestones have been converted though a chemical process to dolomite. Dolomite is a sedimentary rock containing more than 50% of the minerals calcite and dolomite, with dolomite being the most abundant. Dolomite in itself is an interesting mineral find, with an aura of enigma because it has proven impossible to reproduce Dolomite in the laboratory using experimental conditions that replicate the natural environments under which it formed in the past. The mineral is very collectible. Shell formations vary from unconsolidated sand and shell, to loosely cemented shell. This includes the coquina formations found in the coastal areas from St. Johns to Palm Beach Counties. Some sand and clay formations may include shell material; however, there is not enough shell to consider these true limestones. The limestone, shell, and dolomite formations are generally covered by layers of sand and clay. Where the covering is thin or absent, commercial mining of these formations is possible. This includes most areas between the Choctawhatchee River and the Florida Keys. The mineable formations in Florida range in age from the Middle Eocene (42 million years ago) to the Pleistocene (0.5 million years ago). These formations may also be found exposed in caves, stream valleys, sinks, and in the coastal lowlands. Many of the state's best fossil hunting sites can be found in these areas. Many of Florida's unique habitats are the result of the underlying limestone. When rain water mixes with decaying surface vegetation, it becomes mildly acidic. Where the overlaying clay layers are thin or absent, the acidic water dissolves the limestone. Caves, sinks, springs, depressions, and stream and rivers beds are the result of this process. Limestone was first used by Native Americans for the creation of tools and art. Limestone caves and overhangs were used for shelters. Later, the Spanish settlers used the coquina of St. Augustine (1672 - 1696), and the limestone of St. Marks (1759) to build fortifications. When newly exposed the coquina and limerock can be cut with saws and shaped. Exposure to the air allow these materials to case harden over time into long lasting barriers. These structures and the abandoned Spanish mines may be still be seen today. When limestone or dolomite are heated, they lose carbon dioxide and become lime (CaO). Lime from burned oyster shells can be mixed with whole shells and sand to form a cement like material called "tabby." Buildings with walls and floors of tabby may be seen in St. Augustine's history district. Today limestone, shell, and dolomite have wide variety of uses. The following is only a partial list of general uses: • general fill material • crushed stone • aggregate for concrete • rip rap (large stones used to control erosion • Portland cement • cut dimension stone • stucco • fertilizer (aglime) • poultry grit • acid neutralizer • reagent in chemical processes • filler and thickening agent in numerous products • whitener
After parking carefully along the roadside near the posted coords, locate the CaMg(CO3)2. Select the largest of the available samples, and take a photograph of yourself and your GPS with this sample in the picture. Post this photo with your log. Now measure it and determine its volume. Email me this volume using the correct unit of measurement.
Next, find a remnant of a life long past. Take a photograph of this remnant with your GPS in the picture. Post this photograph with your log. Email me the type of life you think you’ve found.