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 coloration.

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