With the help of scientists at Boca Grande’s Mote Marine office,
Sue Erwin and Caroline Clabaugh took these photos of Boca
Grande sand under a strong magnification via a microsope.
62 GASPARILLA ISLAND March/April 2019
moved north to south on each coast while being
eroded and deposited over millions of years of sea
level changes. Carbonates form shell and other
skeletal bits came from the ocean and may be just as
old, although the sea is still making this material. Shells
are broken to bits by the surf, and the shell-munching
actions of sponges, mollusks, crabs and fishes.
The beach sand on tropical islands often looks
white because it is made up of calcium carbonate,
which comes from the shells and skeletons of reefliving
marine organisms, including corals, mollusks and
microorganisms called foraminifera.
Gasparilla Island State Park Manager Rick Argo said
the sand along the beach in Boca Grande is a mixture
of Canaveral Fine Sand, Captiva Fine Sand and
St. Augustine Fine Sand.
If you’ve visited Gasparilla Island, you’ve likely spent some
time with your toes in the sand. But did you ever
wonder exactly what is under your feet when you take
a walk on the beach?
Sand consists of tiny grains of rocks and minerals, and
also miniscule particles of the shells of sea creatures.
Some sand comes from the calcium (a mineral) in
seaweed. Sand can be different colors and the exact
definition of it varies in complex ways.
Florida coastline sand contains silica (silicon dioxide),
usually in the form of quartz. Pure quartz crystal mineral is
ultimately derived from the Southern Appalachian
Mountains. Over many years, rivers carried mineral grains
into the Gulf and further south along the Florida coast. The
quartz sand comes from igneous rock, the kind of rock
that was once molten. Quartz is a very hard mineral just
below the diamond on the hardness scale. The sand has