The Frisco Chert Quarries
Oklahoma is rich in the stone used by Native Americans
to make arrowheads, hoes, knives, scrapers and many other tools.
This stone is known as chert (pronounced churt) and outcroppings
occur in many areas of the state. One of the most important types
of chert to the prehistoric people of eastern Oklahoma is found
in Pontotoc County near Fittstown. It is named for the Frisco formation
of limestone in which it is found.
All cherts are composed of two of the most common
elements on our planet, silicon and oxygen, the same materials that
make up glass. Geologists believe the Frisco cherts were formed
about 400 million years ago when Oklahoma was covered in a warm,
shallow sea. Many simple marine animals, including sponges, extract
silicon compounds from seawater to form their skeletons. As these
animals died in the ancient oceans, their glassy skeletons settled
to the bottom where they accumulated and were eventually transformed
into rocks like chert. Parts of ancient sponges, known as spicules,
can be seen in the Frisco cherts.
Cherts are extremely hard rocks that tend to fracture
in a conchoidal (shell-like) pattern. This quality allows it to
be worked into tools with sharp, durable edges. Prehistoric people
quarried cherts and traded some highly-prized ones over hundreds
of miles. Some cherts, like Frisco, also became even easier to work
with when fired at high temperatures in prehistoric rock ovens.
Heat-treated Frisco chert is shinier and often has a pink or blue
The Frisco chert outcroppings were visited for thousands
of years by prehistoric toolmakers like those from the Raulston-Rogers
site and the Primrose and Stillman Pit
sites. The chips and debris from their work as they fashioned tools
can still be seen in the Frisco quarry areas.
Examples of Frisco chert