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.